something dumb on bibtex entry format,

[Mike Marchywka]

I'm finally moving my bibtex scraping script to c++ and cleaning up a lot
of stuff. I validate a foreign or scraped bibtex entry using latex run on
a test document and my own parser. Its unlikely my parser conforms to 
bibtex requirements exactly so I want to do both. I found what appears
to be an old test case and it still does not make sense. The question
seems to be about backslashes preceding a terminating right brace.
Sometimes they are ok, others not. The test files are xxx.tex and xxx.bib
as shown below.  If I put a backslash on the "month" line before the right brace
it seems to work ( originally there was an abstract entry with the problem but
I deleted it for space and clarity ), 
    month = {2015-09-08 00:00:00 \},

However, doing it on the publisher line fails,

    publisher = {John Wiley \& Sons, Ltd \},




 cat /tmp/xxx.tex
\documentclass{article}
\begin{document}
\nocite{*}
\bibliographystyle{plain}
\bibliography{xxx}
\end{document}
marchywka at happy:/home/documents/cpp/proj/toobib/junk$ cat /tmp/xxx.bib
% programmatically fixed probably bu toobib
% loaded from bbb written on 2019-11-02:17:33:45
%0 prior 0
@inproceedings{18538,
    address = {Boston, MA, USA},
    author = {Silva, J. C. and Aroso, I. M. and Mano, F. and S{\'a}-Nogueira, I. and Barreiros, S. and Reis, R. L. and Paiva, A. and Duarte, A. R. C.},
    doi = {10.1089/ten.tea.2015.5000.abstracts},
    journal = {Tissue Engineering Part A},
    keywords = {Drug delivery systems, green chemistry, Therapeutic deep eutectic solvents},
    month = {2015-09-08 00:00:00 },
    publisher = {John Wiley \& Sons, Ltd },
    title = { Therapeutic deep eutectic solvents as solubility enhancers fordifferent active pharmaceutical ingredients},
    url = {http://online.liebertpub.com/doi/full/10.1089/ten.tea.2015.5000.abstracts},
    year = {2015}
}
marchywka at happy:/home/documents/cpp/proj/toobib/junk$ 


I run 3 times, latex, bibtex, and latex again, then grep for error, output, and warning
giving the following lines in the two cases, 

No pages of output .
Warning - - empty booktitle in 18538
( There was 1 warning )
. / xxx . bbl : 9 : = = > Fatal error occurred , no output PDF file produced !

versus, 

=No pages of output .
Warning - - empty booktitle in 18538
( There was 1 warning )
LaTeX Warning : Label ( s ) may have changed . Rerun to get cross - references right .
Output written on xxx . pdf ( 1 page , 28937 bytes ) .


What is the backslash before the brace supposed to do or is there something silly I'm
missing? Thanks.


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 Mike Marchywka 306 Charles Cox Drive Canton, GA 30115
 2295 Collinworth  Drive Marietta GA 30062.  formerly 487 Salem Woods Drive Marietta GA 30067 404-788-1216 (C)<- leave message 989-348-4796 (P)<- emergency