Welcome to sphinxcontrib-bibtex’s documentation!¶
- Release
1.0.0
- Date
Sep 23, 2019
Contents¶
Getting Started¶
Overview¶
A Sphinx extension for BibTeX style citations.
This extension allows BibTeX
citations to be inserted into documentation generated by
Sphinx, via
a bibliography
directive, and a cite
role, which
work similarly to LaTeX’s thebibliography
environment
and \cite
command.
For formatting, the extension relies on pybtex written by Andrey Golovizin. The extension is inspired by Matthew Brett’s bibstuff.sphinxext.bibref.
Installation¶
Install the module with pip install sphinxcontrib-bibtex
, or from
source using python setup.py install
. Then add:
extensions = ['sphinxcontrib.bibtex']
to your project’s Sphinx configuration file conf.py
.
Minimal Example¶
In your project’s documentation, you can then write for instance:
See :cite:`1987:nelson` for an introduction to non-standard analysis.
.. bibliography:: refs.bib
where refs.bib would contain an entry:
@Book{1987:nelson,
author = {Edward Nelson},
title = {Radically Elementary Probability Theory},
publisher = {Princeton University Press},
year = {1987}
}
Usage¶
Roles and Directives¶
-
:cite:
¶ Create a citation to a bibliographic entry. For example:
See :cite:`1987:nelson` for an introduction to non-standard analysis.
which would be equivalent to the following LaTeX code:
See \cite{1987:nelson} for an introduction to non-standard analysis.
Multiple comma-separated keys can be specified at once:
See :cite:`1987:nelson,2001:schechter`.
-
.. bibliography::
refs.bib [...]
¶ Create bibliography for all cited references. The
all
flag forces all references to be included (equivalent to\nocite{*}
in LaTeX). Thenotcited
flag causes all references that were not cited to be included. Thecited
flag is recognized as well but is entirely optional. For example:.. bibliography:: refs.bib :cited:
which would be roughly equivalent to the following LaTeX code:
\begin{thebibliography}{1} \bibitem{1987:nelson} Edward~Nelson \newblock {\em Radically Elementary Probability Theory}. \newblock Princeton University Press, 1987. \end{thebibliography}
Warning
Sphinx may not be able to create an entry for
cite
keys when yourbibliography
directive resides in a different document; see Unresolved Citations Across Documents for more information and workarounds.You can also pick a bibliography style, using the
style
option. Thealpha
style is the default. Other supported styles areplain
,unsrt
, andunsrtalpha
... bibliography:: refs.bib :style: unsrt
Warning
Sphinx will attempt to resolve references to the bibliography across all documents, so you must take care that no citation key is included more than once.
You can also set the encoding of the bibliography files, using the
encoding
option... bibliography:: refs.bib :encoding: latin
LaTeX control characters are automatically converted to unicode characters (for instance, to convert
\'e
intoé
). Be sure to write\%
when you intend to format a percent sign.
Advanced Features¶
Bullet Lists and Enumerated Lists¶
New in version 0.2.4.
You can change the type of list used for rendering the bibliography. By default, a paragraph of standard citations is generated. However, instead, you can also generate a bullet list, or an enumerated list.
.. bibliography:: refs1.bib
:list: bullet
:all:
.. bibliography:: refs2.bib
:list: enumerated
:all:
Note that citations to these types of bibliography lists will not be resolved.
For enumerated lists, you can also specify the type (default is
arabic
), and the start of the sequence (default is 1
).
.. bibliography:: refs2.bib
:list: enumerated
:enumtype: upperroman
:start: 3
:all:
The enumtype can be any of
arabic
(1, 2, 3, …),
loweralpha
(a, b, c, …),
upperalpha
(A, B, C, …),
lowerroman
(i, ii, iii, …), or
upperroman
(I, II, III, …).
The start can be any positive integer (1, 2, 3, …) or
continue
if you wish the enumeration to continue from the last
bibliography
directive.
This is helpful if you split up your bibliography but
still want to enumerate the entries continuously.
Label Prefixing¶
New in version 0.2.5.
If you have multiple bibliographies, and experience duplicate labels,
use the labelprefix
option.
.. rubric:: References
.. bibliography:: refs.bib
:cited:
:labelprefix: A
.. rubric:: Further reading
.. bibliography:: refs.bib
:notcited:
:labelprefix: B
Key Prefixing¶
New in version 0.3.3.
If you have multiple bibliographies, and you would like entries to be
repeated in different documents, then use the keyprefix
option.
For example, suppose you have two documents, and you would like to cite
boole1854
in both of these doucments, with the bibliography entries
showing in both of the documents. In one document you could have:
See :cite:`a-boole1854`
.. bibliography:: refs.bib
:labelprefix: A
:keyprefix: a-
whilst in the other document you could have:
See :cite:`b-boole1854`
.. bibliography:: refs.bib
:labelprefix: B
:keyprefix: b-
The bibliographies will then both generate an entry for boole1854
,
with links and backlinks as expected.
See also
Filtering¶
New in version 0.2.7.
Whilst the cited
, all
, and notcited
options
will cover many use cases,
sometimes more advanced selection of bibliographic entries is desired.
For this purpose, you can use the filter
option:
.. bibliography:: refs.bib
:list: bullet
:filter: author % "Einstein"
The string specified in the filter option must be a valid Python expression.
Note
The expression is parsed using ast.parse()
and then evaluated using an ast.NodeVisitor
,
so it should be reasonably safe against malicious code.
The filter expression supports:
The boolean operators
and
,or
.The unary operator
not
.The comparison operators
==
,<=
,<
,>=
, and>
.Regular expression matching using the
%
operator, where the left hand side is the string to be matched, and the right hand side is the regular expression. Matching is case insensitive. For example:.. bibliography:: refs.bib :list: bullet :filter: title % "relativity"
would include all entries that have the word “relativity” in the title.
Note
The implementation uses
re.search()
.Single and double quoted strings, such as
'hello'
or"world"
.Set literals, such has
{"hello", "world"}
, as well as the set operators&
,|
,in
, andnot in
.New in version 0.3.0.
Various identifiers, such as:
type
is the entry type, as a lower case string (i.e."inproceedings"
).key
is the entry key, as a lower case string (this is because keys are considered case insensitive).cited
evaluates toTrue
if the entry was cited in the document, and toFalse
otherwise.docname
evaluates to the name of the current document.New in version 0.3.0.
docnames
evaluates to a set of names from which the entry is cited.New in version 0.3.0.
True
andFalse
.author
is the entry string of authors in standard format (last, first), separated by “and”.editor
is similar toauthor
but for editors.Any other (lower case) identifier evaluates to a string containing the value of the correspondingly named field, such as
title
,publisher
,year
, and so on. If the item is missing in the entry then it evaluates to the empty string. Here is an example of how one would typically write an expression to filter on an optional field:.. bibliography:: refs.bib :list: bullet :filter: cited and year and (year <= "2003")
which would include all cited entries that have a year that is less or equal than 2003; any entries that do not specify a year would be omitted.
Local Bibliographies¶
Both the keyprefix
and filter
options can be used
to achieve local bibliographies.
The filter
system for local bibliographies is the simplest one to
use, but offers the least amount of flexibility. In particular, it
can only be used if no citation key is used in more than one
document. This is not always satisfied. If you need to cite the same
reference in multiple documents with references to multiple local
bibliographies, use the keyprefix
system; see
Key Prefixing.
To create a bibliography that includes only citations that were cited in the current document, use the following filter:
.. bibliography:: refs.bib
:filter: docname in docnames
More generally, you can create bibliographies for citations that were cited from specific documents only:
.. bibliography:: refs.bib
:filter: {"doc1", "doc2"} & docnames
This bibliography will include all citations that were cited from
doc1.rst
or doc2.rst
. Another hypothetical example:
.. bibliography:: refs.bib
:filter: cited and ({"doc1", "doc2"} >= docnames)
This bibliography will include all citations that were cited
in doc1.rst
or doc2.rst
, but nowhere else.
Custom Formatting, Sorting, and Labelling¶
pybtex
provides a very powerful way to create and register new
styles, using setuptools entry points,
as documented here: http://docs.pybtex.org/api/plugins.html
Simply add the following code to your conf.py
:
from pybtex.style.formatting.unsrt import Style as UnsrtStyle
from pybtex.style.template import toplevel # ... and anything else needed
from pybtex.plugin import register_plugin
class MyStyle(UnsrtStyle):
def format_XXX(self, e):
template = toplevel [
# etc.
]
return template.format_data(e)
register_plugin('pybtex.style.formatting', 'mystyle', MyStyle)
Now mystyle
will be available to you as a formatting style:
.. bibliography:: refs.bib
:style: mystyle
An minimal example is available here: https://github.com/mcmtroffaes/sphinxcontrib-bibtex/tree/develop/test/custom_style
The formatting code uses a very intuitive template engine.
The source code for unsrt
provides many great examples:
https://bitbucket.org/pybtex-devs/pybtex/src/master/pybtex/style/formatting/unsrt.py?at=master&fileviewer=file-view-default
The above example only demonstrates a custom formatting style plugin.
It is also possible to register custom author/editor naming plugins
(using the pybtex.style.names
group)
labelling plugins
(using the pybtex.style.labels
group),
and sorting plugins
(using the pybtex.style.sorting
group).
A few minimal examples demonstrating how to create a custom label styles
are available here:
* https://github.com/mcmtroffaes/sphinxcontrib-bibtex/tree/develop/test/issue77
* https://github.com/mcmtroffaes/sphinxcontrib-bibtex/tree/develop/test/custom_labels
Known Issues and Workarounds¶
Encoding: Percent Signs¶
When using the LaTeX codec (which is by default), be sure to write
\%
for percent signs at all times (unless your file contains a
genuine comment), otherwise the bibtex lexer will ignore the remainder
of the line.
If you don’t want any LaTeX symbols to be reinterpreted as unicode,
use the option :encoding: utf
(without the latex+
prefix).
Unresolved Citations Across Documents¶
If you cite something that has its bibliography in another document, then, at the moment, the extension may, or may not, realise that it has to add this citation. There are a few ways to work around this problem:
Use the option
:all:
in thebibliography
directive (which will simply cause all entries to be included).Ensure that the
bibliography
directive is processed after allcite
s. Sphinx appears to process files in an alphabetical manner. For instance, in case you have only one file containing abibliography
directive, simply name that filezreferences.rst
.
Hopefully, this limitation can be lifted in a future release.
Duplicate Labels When Using :style: plain
¶
With :style: plain
, labels are numerical,
restarting at [1]
for each bibliography
directive.
Consequently, when inserting multiple bibliography
directives
with :style: plain
,
you are bound to get duplicate labels for entries.
There are a few ways to work around this problem:
Use a single bibliography directive for all your references.
Use the
labelprefix
option, as documented above.Use a style that has non-numerical labelling, such as
:style: alpha
.
Mismatch Between Output of HTML and LaTeX Backends¶
Sphinx’s LaTeX writer currently collects all citations together, and puts them on a separate page, with a separate title, whereas the html writer puts citations at the location where they are defined. This issue will occur also if you use regular citations in Sphinx: it has nothing to do with sphinxcontrib-bibtex per se.
To get a closer match between the two outputs, you can tell Sphinx to generate a rubric title only for html:
.. only:: html
.. rubric:: References
.. bibliography:: refs.bib
This code could be placed in your zreferences.rst
.
Alternatively, to remove the bibliography section title from the LaTeX output, you can add the following to your LaTeX preamble:
\usepackage{etoolbox}
\patchcmd{\thebibliography}{\section*{\refname}}{}{}{}
Extension API¶
Sphinx Interface¶
-
sphinxcontrib.bibtex.
setup
(app)[source]¶ Set up the bibtex extension:
register config values
register directives
register nodes
register roles
register transforms
connect events to functions
- Parameters
app (
sphinx.application.Sphinx
) – The sphinx application.
-
sphinxcontrib.bibtex.
init_bibtex_cache
(app)[source]¶ Create
app.env.bibtex_cache
if it does not exist yet.- Parameters
app (
sphinx.application.Sphinx
) – The sphinx application.
-
sphinxcontrib.bibtex.
purge_bibtex_cache
(app, env, docname)[source]¶ Remove all information related to docname from the cache.
- Parameters
app (
sphinx.application.Sphinx
) – The sphinx application.env (
sphinx.environment.BuildEnvironment
) – The sphinx build environment.
-
sphinxcontrib.bibtex.
process_citations
(app, doctree, docname)[source]¶ Replace labels of citation nodes by actual labels.
- Parameters
app (
sphinx.application.Sphinx
) – The sphinx application.doctree (
docutils.nodes.document
) – The document tree.docname (
str
) – The document name.
-
sphinxcontrib.bibtex.
process_citation_references
(app, doctree, docname)[source]¶ Replace text of citation reference nodes by actual labels.
- Parameters
app (
sphinx.application.Sphinx
) – The sphinx application.doctree (
docutils.nodes.document
) – The document tree.docname (
str
) – The document name.
-
sphinxcontrib.bibtex.
check_duplicate_labels
(app, env)[source]¶ Check and warn about duplicate citation labels.
- Parameters
app (
sphinx.application.Sphinx
) – The sphinx application.env (
sphinx.environment.BuildEnvironment
) – The sphinx build environment.
New Doctree Roles¶
New Doctree Nodes¶
-
class
sphinxcontrib.bibtex.nodes.
bibliography
(rawsource='', *children, **attributes)[source]¶ Node for representing a bibliography. Replaced by a list of citations by
BibliographyTransform
.
New Doctree Directives¶
-
class
sphinxcontrib.bibtex.directives.
BibliographyDirective
(name, arguments, options, content, lineno, content_offset, block_text, state, state_machine)[source]¶ Class for processing the
bibliography
directive.Parses the bibliography files, and produces a
bibliography
node.See also
Further processing of the resulting
bibliography
node is done byBibliographyTransform
.-
run
()[source]¶ Process .bib files, set file dependencies, and create a node that is to be transformed to the entries of the bibliography.
-
process_bibfile
(bibfile, encoding)[source]¶ Check if
env.bibtex_cache.bibfiles[bibfile]
is still up to date. If not, parse the bibfile (seeupdate_bibfile_cache()
), and store parsed data in the bibtex cache.- Parameters
bibfile (
str
) – The bib file name.- Returns
The parsed bibliography data.
- Return type
pybtex.database.BibliographyData
-
update_bibfile_cache
(bibfile, mtime, encoding)[source]¶ Parse bibfile (see
parse_bibfile()
), and store the parsed data, along with modification time mtime, in the bibtex cache.- Parameters
bibfile (
str
) – The bib file name.mtime (
float
) – The bib file’s modification time.
- Returns
The parsed bibliography data.
- Return type
pybtex.database.BibliographyData
-
-
sphinxcontrib.bibtex.directives.
process_start_option
(value)[source]¶ Process and validate the start option value of a
bibliography
directive. If value iscontinue
then this function returns -1, otherwise value is converted into a positive integer.
New Doctree Transforms¶
-
class
sphinxcontrib.bibtex.transforms.
BibliographyTransform
(document, startnode=None)[source]¶ Bases:
docutils.transforms.Transform
A docutils transform to generate citation entries for bibliography nodes.
-
default_priority
= 10¶ Priority of the transform. See http://docutils.sourceforge.net/docs/ref/transforms.html
-
apply
()[source]¶ Transform each
bibliography
node into a list of citations.
-
Cached Information¶
Classes and methods to maintain any information that is stored outside the doctree.
-
class
sphinxcontrib.bibtex.cache.
Cache
[source]¶ Global bibtex extension information cache. Stored in
app.env.bibtex_cache
, so must be picklable.-
bibfiles
= None¶ A
dict
mapping .bib file names (relative to the top source folder) toBibfileCache
instances.
-
get_all_cited_keys
()[source]¶ Yield all citation keys, sorted first by document (alphabetical), then by citation order in the document.
-
get_bibliography_cache
(docname, id_)[source]¶ Return
BibliographyCache
with id id_ in document docname.
-
get_bibliography_entries
(docname, id_, warn)[source]¶ Return filtered bibliography entries, sorted by citation order.
-
get_cited_docnames
(key)[source]¶ Return the docnames from which the given key is cited.
- Parameters
key (
str
) – The citation key.
-
purge
(docname)[source]¶ Remove all information related to docname.
- Parameters
docname (
str
) – The document name.
-
set_bibliography_cache
(docname, id_, bibcache)[source]¶ Register bibcache (
BibliographyCache
) with id id_ for document docname.
-
-
class
sphinxcontrib.bibtex.cache.
BibfileCache
[source]¶ Contains information about a parsed .bib file.
-
data
¶ A
pybtex.database.BibliographyData
containing the parsed .bib file.
-
-
class
sphinxcontrib.bibtex.cache.
BibliographyCache
[source]¶ Contains information about a bibliography directive.
-
bibfiles
¶ A
list
ofstr
s containing the .bib file names (relative to the top source folder) that contain the references.
-
style
¶ The bibtex style.
-
list_
¶ The list type.
-
enumtype
¶ The sequence type (only used for enumerated lists).
-
start
¶ The first ordinal of the sequence (only used for enumerated lists).
-
labels
¶ Maps citation keys to their final labels.
-
labelprefix
¶ This bibliography’s string prefix for pybtex generated labels.
-
keyprefix
¶ This bibliography’s string prefix for citation keys.
-
Changes¶
1.0.0 (20 September 2019)¶
Drop Python 2.7 and 3.4 support (as upstream sphinx has dropped support for these as well).
Add Python 3.8 support (contributed by hroncok).
Update for Sphinx 2.x, and drop Sphinx 1.x support (as there is too much difference between the two versions).
Non-bibtex citations will now no longer issue warnings (fix contributed by chrisjsewell).
Switch to codecov for coverage reporting.
0.4.2 (7 January 2018)¶
Drop Python 3.3 support, add Python 3.7 support.
Work around issue with sphinx-testing on Fedora (reported by jamesjer in issue #157, fix contributed by mitya57 in pull request #158).
0.4.1 (28 November 2018)¶
Disable tinkerer test due to upstream bug.
Remove crossref test due to changed upstream behaviour in pybtex.
Fix latex test to match new upstream code generation.
Fix documentation of encoding option (contributed by Kai Mühlbauer).
Migrate to sphinx.util.logging in favour of old deprecated logging method.
0.4.0 (19 April 2018)¶
Remove latexcodec and curly bracket strip functionality, as this is now supported by pybtex natively (see issue #127, reported by erosennin).
Fix tests failures with Sphinx 1.7 (see pull request #136, reported and fixed by mitya57).
0.3.6 (25 September 2017)¶
Real fix for issue #111 (again reported by jamesjer).
Fix test regressions due to latest Sphinx updates (see issues #115, #120, #121, and #122, reported by ndarmage and ghisvail).
Fix test regressions on ascii locale (see issue #121, reported by ghisvail).
Support and test Python 3.6.
0.3.5 (22 February 2017)¶
Fix extremely high memory usage when handling large bibliographies (reported by agjohnson, see issue #102).
Fix tests for Sphinx 1.5.1 (see issue #111, reported by jamesjer).
0.3.4 (20 May 2016)¶
Document LaTeX workaround for
:cite:
in figure captions (contributed by xuhdev, see issue #92 and pull request #93).Add
bibtex_default_style
config value to override the default bibliography style (see issue #91 and pull request #97).Support Python 3.5 (see issue #100).
0.3.3 (23 October 2015)¶
Add per-bibliography key prefixes, enabling local bibliographies to be used in isolation from each other (see issue #87, reported by marscher).
Documentation now points to new location of pybtex on bitbucket.
Simplified testing code by using the new sphinx_testing package.
0.3.2 (20 March 2015)¶
Document how to create custom label styles (see issue #77, reported by tino).
Disable parallel_read_safe for Sphinx 1.3 and later (see issue #80, reported by andreacassioli).
0.3.1 (10 July 2014)¶
Fix for
type_.lower()
bug: pybtex 0.18 expects type to be a string (this fixes issue #68 reported by jluttine).
0.3.0 (4 May 2014)¶
BACKWARD INCOMPATIBLE The alpha style is now default, so citations are labelled in a way that is more standard for Sphinx. To get the old behaviour back, add
:style: plain
to your bibliography directives.BACKWARD INCOMPATIBLE
is_cited()
has been removed. Useget_cited_docnames()
instead, which will return an empty list for keys that are not cited.Improved support for local bibliographies (see issues #52, #62, and #63; test case provided by Boris Kheyfets):
New
docname
anddocnames
filter identifiers.Filter expressions now also support set literals and the operators
in
,not in
,&
, and|
.
See documentation for details.
Multiple comma-separated citation keys per cite command (see issue #61, suggested by Boris Kheyfets).
Add support for pypy and Python 3.4.
Drop support for Python 2.6 and Python 3.2.
Drop 2to3 and instead use six to support both Python 2 and 3 from a single code base.
Simplify instructions for custom styles.
Various test suite improvements.
0.2.9 (9 October 2013)¶
Upgrade to the latest pybtex-docutils to produce more optimal html output (specifically: no more nested
<span>
s).Remove latex codec code, and rely on latexcodec package instead.
FilterVisitor
has been removed from the public API. Useget_bibliography_entries()
instead.Fix upstream Sphinx bug concerning LaTeX citation hyperlinks (contributed by erikb85; see pull request #45).
Fix most pylint warnings, refactor code.
0.2.8 (7 August 2013)¶
Use pybtex-docutils to remove dependency on pybtex.backends.doctree.
0.2.7 (4 August 2013)¶
Integrate with coveralls.io, first release with 100% test coverage.
Minor bug fixes and code improvements.
Remove ordereddict dependency for Python 2.7 and higher (contributed by Paul Romano, see pull requests #27 and #28).
New
:filter:
option for advanced filtering (contributed by d9pouces, see pull requests #30 and #31).Refactor documentation of advanced features.
Document how to create custom pybtex styles (see issues #25, #29, and #34).
Code is now mostly pep8 compliant.
0.2.6 (2 March 2013)¶
For unsorted styles, citation entries are now sorted in the order they are cited, instead of following the order in the bib file, to reflect more closely the way LaTeX handles unsorted styles (addresses issue #15).
Skip citation label warnings on Sphinx [source] links (issue #17, contributed by Simon Clift).
0.2.5 (18 October 2012)¶
Duplicate label detection (issue #14).
New
:labelprefix:
option to avoid duplicate labels when having multiple bibliographies with a numerical label style (addresses issue #14).
0.2.4 (24 August 2012)¶
New options for the bibliography directive for rendering the bibliography as bullet lists or enumerated lists:
:list:
,:enumtype:
, and:start:
.Minor latex codec fixes.
Turn exception into warning when a citation cannot be relabeled (fixes issue #2).
Document LaTeX encoding, and how to turn it off (issue #4).
Use pybtex labels (fixes issue #6 and issue #7).
Cache tracked citation keys and labels, and bibliography enumeration counts (fixes issues with citations in repeated Sphinx runs).
Bibliography ids are now unique across documents (fixes issue that could cause the wrong bibliography to be inserted).
The plain style is now the default (addresses issue #9).
0.2.3 (30 July 2012)¶
Document workaround for Tinkerer (issue #1).
Use tox for testing.
Full 2to3 compatibility.
Document supported versions of Python (2.6, 2.7, 3.1, and 3.2).
0.2.2 (6 July 2012)¶
Documentation and manifest fixes.
0.2.1 (19 June 2012)¶
First public release.
License¶
Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:
Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS “AS IS” AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.