This is pdfTeX, Version 3.1415926-1.40.11 (TeX Live 2010) (format=pdflatex 2011.5.4) 23 SEP 2012 23:49 entering extended mode \write18 enabled. file:line:error style messages enabled. %&-line parsing enabled. **comandiamsIt (./comandiamsIt LaTeX2e <2009/09/24> Babel and hyphenation patterns for english, dumylang, nohyphenation, ge rman-x-2009-06-19, ngerman-x-2009-06-19, ancientgreek, ibycus, arabic, armenian , basque, bulgarian, catalan, pinyin, coptic, croatian, czech, danish, dutch, u kenglish, usenglishmax, esperanto, estonian, farsi, finnish, french, galician, german, ngerman, swissgerman, monogreek, greek, hungarian, icelandic, assamese, bengali, gujarati, hindi, kannada, malayalam, marathi, oriya, panjabi, tamil, telugu, indonesian, interlingua, irish, italian, kurmanji, lao, latin, latvian, lithuanian, mongolian, mongolianlmc, bokmal, nynorsk, polish, portuguese, roma nian, russian, sanskrit, serbian, slovak, slovenian, spanish, swedish, turkish, turkmen, ukrainian, uppersorbian, welsh, loaded. \c@teorema=\count79 ./comandiamsIt:66: LaTeX Error: No counter 'section' defined. See the LaTeX manual or LaTeX Companion for explanation. Type H for immediate help. ... l.66 \newtheorem{teorema}{Teorema}[section] ? ./comandiamsIt:66: Emergency stop. ... l.66 \newtheorem{teorema}{Teorema}[section] Your command was ignored. Type I to replace it with another command, or to continue without it. Here is how much of TeX's memory you used: 63 strings out of 493747 534 string characters out of 3143547 49070 words of memory out of 3000000 3453 multiletter control sequences out of 15000+200000 3824 words of font info for 15 fonts, out of 3000000 for 9000 714 hyphenation exceptions out of 8191 8i,0n,11p,85b,14s stack positions out of 5000i,500n,10000p,200000b,50000s ./comandiamsIt:66: ==> Fatal error occurred, no output PDF file produced!