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Trying to get my dissertaion sorted (due in a few hours) and I keep getting this error:

! Missing $ inserted.
<inserted text> 
l.190 ... pp. 225--236, 10.1007/978-0-387-68772-8_
                                                  18. [Online].

Really struggling to sort it out.

I'm fairly new to LaTeX.

Edit: This is 189-204 of the bibtex

 author = {Davis, Alan and Dieste, Oscar and Hickey, Ann and Juristo, Natalia and Moreno, Ana M.},
 title = {Effectiveness of Requirements Elicitation Techniques: Empirical Results Derived from a Systematic Review},
 booktitle = {Proceedings of the 14th IEEE International Requirements Engineering Conference},
 series = {RE '06},
 year = {2006},
 isbn = {0-7695-2555-5},
 pages = {176--185},
 numpages = {10},
 url = {http://dx.doi.org/10.1109/RE.2006.17},
 doi = {10.1109/RE.2006.17},
 acmid = {1174006},
 publisher = {IEEE Computer Society},
 address = {Washington, DC, USA},
 keywords = {Systematic review, software engineering, elicitation techniques, empirical studies},

Please help!

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You need to supply more information. What does your code look like around line 190 of the file? Seems like an entry in a bibliography. Edit your question and include that detail (perhaps the entire bibliography?). – Werner Sep 11 '12 at 23:58
The solution that avoids the error and liberates from having to change the urls is to ``` \usepackage{url} ``` as suggested here. – Ioannis Filippidis Oct 7 '14 at 8:44
up vote 29 down vote accepted

The line number in the error message is the line of the .bbl file that is generated by bibtex, it is not the line of the .bib file. Therefore the question quotes the wrong lines. The line in the error message contains:

pp. 225--236, 10.1007/978-0-387-68772-8_18. [Online].

Therefore I think the entry in the .bib file contains

doi = {10.1007/978-0-387-68772-8_18},

It seems the DOI numbers are not well supported. The prefix doi: is missing:


Or as URL:


Also special characters like _ are not well supported. The _ causes the trouble. Make a minimal example (MWE) that shows, how the doi entries in the .bib file are handled in your document.

If there are no special macros that handle the doi numbers, then you can try \_ instead of _ in the .bib file.

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Cheers for the help guys, bit stressed with the deadline looming. Thanks again. – Jon Sep 12 '12 at 0:37
Why should the prefix doi: be required for the DOI field? A doi number always starts with 10, not with doi: – koppor Jun 22 '15 at 19:55

The problem is the underscore _ in a doi. It occurs in line 190 of the LaTeX file (or in the .bbl) not in the .bib file.

Search for 10.1007/978-0-387-68772-8_18 in your .bib file. You can use the url package and enclose the entry in \url{10.1007/978-0-387-68772-8_18} to avoid the error. Alternatively you can use a bibtex style that knows about dois.

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It might also be necessary to delete and remake the .bbl file. (I'm adding that for other readers. Learned it the hard way.) – Mars Oct 8 '15 at 21:43

Another solution could be to drop the whole "_18" as it says just "chapter 18". If you write "10.1007/978-0-387-68772-8" rather than "10.1007/978-0-387-68772-8_18" the reader will still be referred to the right book, but not to chapter 18 within it.

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What Werner and Gonzalo said would indeed be very helpful. From the limited info given however, I guess LaTeX struggles with the _ in the line, since it normally sees that as a subscript indicator and only expects it in math mode.

A very short solution (and impossible to say if that works without taking a look at the offending code) is to escape the underscore ("_"), by placing a backslash before it.

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Which underscore? – Jon Sep 12 '12 at 0:15


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This should be the accepted answer; this completely solves the problem, whereas the currently-accepted answer merely explains the problem. – Tom Church 2 days ago

To get rid of the underscore ("_"), you can use shortdoi.org and doi:10/djzjd6 instead of doi:10.1007/978-0-387-68772-8_18, which is also nice when your readers need to type the doi from a printed version of your thesis instead of being able to click at it in an electronic document.

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Another future-proof answer, albeit rather tedious, is suggested here:

Change all occurrences of _ in the URL field of your .bib file to their html character code equivalent %5F

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Try using in the preamble \usepackage{url}. This should clear the problem.

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worked for me! I wonder why it got downvoted? It doesn't have any analysis or explanation of the problem, but it seems like the quickest fix. I am wary of changing my .bib file in case bibtex starts handling underscores correctly (i.e. without needing an escape character) and prints \_ into the bibliography – craq Apr 13 at 9:44
Didn't work for me... – Roly Jun 20 at 9:46

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