This is pdfTeX, Version 3.1415926-2.4-1.40.13 (TeX Live 2012) (format=pdflatex 2012.6.30) 28 MAR 2013 18:12 entering extended mode restricted \write18 enabled. file:line:error style messages enabled. %&-line parsing enabled. **commands.tex (./commands.tex LaTeX2e <2011/06/27> Babel and hyphenation patterns for english, dumylang, nohyphenation, ge rman-x-2012-05-30, ngerman-x-2012-05-30, afrikaans, ancientgreek, ibycus, arabi c, armenian, basque, bulgarian, catalan, pinyin, coptic, croatian, czech, danis h, dutch, ukenglish, usenglishmax, esperanto, estonian, ethiopic, farsi, finnis h, french, friulan, galician, german, ngerman, swissgerman, monogreek, greek, h ungarian, icelandic, assamese, bengali, gujarati, hindi, kannada, malayalam, ma rathi, oriya, panjabi, tamil, telugu, indonesian, interlingua, irish, italian, kurmanji, latin, latvian, lithuanian, mongolian, mongolianlmc, bokmal, nynorsk, polish, portuguese, romanian, romansh, russian, sanskrit, serbian, serbianc, s lovak, slovenian, spanish, swedish, turkish, turkmen, ukrainian, uppersorbian, welsh, loaded. ./commands.tex:9: Undefined control sequence. l.9 \DeclareMathOperator {\re}{Re} ? ./commands.tex:9: Emergency stop. l.9 \DeclareMathOperator {\re}{Re} End of file on the terminal! Here is how much of TeX's memory you used: 15 strings out of 493488 166 string characters out of 3141326 49432 words of memory out of 3000000 3422 multiletter control sequences out of 15000+200000 3640 words of font info for 14 fonts, out of 3000000 for 9000 957 hyphenation exceptions out of 8191 7i,0n,6p,56b,8s stack positions out of 5000i,500n,10000p,200000b,50000s ./commands.tex:9: ==> Fatal error occurred, no output PDF file produced!