This is question is actually a question to an answer from here, but since my rep is too low, I have no other option than to ask it like this. The question from that link goes like this:

I have a bibliography that mixes every reference type (mostly books and articles together). Now, I would love to be able to separate only the articles from the rest and display them under a separate bibliography subtitle, e.g. "Articles". Is this in any way possible?

someone called Zun answered the question that it is possible with biblatex, and a working example would be this:

    author       = {Bevel Lemelisk and Wilhuff Tarkin and Darth Vader and Darth Sidious},
    title        = {Death Star},
    howpublished = {Alderaan and Yavin 4},
    year         = {0 BBY}
    author       = {Bevel Lemelisk and Wilhuff Tarkin and Darth Vader and Darth Sidious},
    title        = {Death Star II},
    howpublished = {Endor},
    year         = {4 ABY}
    author       = {Abc, D.},
    title        = {The Letter Fantasies},
    year         = 1492,
    keywords     = {one}
    author       = {Efg, H.},
    title        = {Alphabet Soup},
    year         = 1942,
    keywords     = {two}
%   style=authoryear, % uncomment to display author-year
  not type=article
They first built \emph{Death Star}~\autocite{death-star}.

The design flaw was found in \autocite[Lemelisk et al., Chapter 3, p. 123][]{death-star}.

To address the flaw, they designed \emph{Death Star 2}~\autocite{death-star-2}
that featured many smaller diameter heat exhaust vents.

Read the letter fantasies \cite{abc} or stories from the a-soup \cite{efg}.
\printbibliography[heading=subbibliography,title={Other Sources},filter=other]

and this works flawlessly. As long as the entry-type is written with small letters. However, I use JabRef, and it formats my references with a capital letter, like @Online, @Book etc. In Zuns working example above, the entry @Book is with a capital letter. Try substituting @article with @Book. Suddenly it gives the error:

./untitled.tex:48: LaTeX Warning: Empty bibliography on input line 48.

Since all of my entries are with a capital letter, this is most unfortunate. Is there anything that can be done about this? Thank you for your time.

  • Welcome to TeX.SX! Well, it's a warning only... – user31729 Jan 19 '15 at 22:14
  • Thank you :) Well, yes, it is a warning. But it is warning with the result that the bibliography that it warns about doesn't get printed, only the other bib, with the filter=other. – emilBeBri Jan 20 '15 at 0:56
  • 2
    I cannot reproduce your problem. I tried all lowercase @<whatever>, all uppercase, some uppercase and some lowercase; I switched the first @article to @Book. No problems (after running, of course, the full sequence of pdflatex, biber, pdflatex). You might need to elaborate. My versions: biblatex v2.9a and biber 1.9. – jon Jan 20 '15 at 3:47
  • It works like a charm here as well. (biblatex 2.9a with biber 1.9 on an up-to-date MikTeX.) What I noticed though is that your bibcheck construction is superfluous you can just use nottype=article instead of filter=other. – moewe Jan 20 '15 at 6:45
  • Okay, that is strange. Just updated texlive, I have biblatex 2.9a and biber 1.9 on my lubuntu 14.04 system. will try on a w7 machine later today, see if it's the same. Moewe: nice tip with the nottype instead, thank you! – emilBeBri Jan 20 '15 at 12:20