! Undefined control sequence. \documentclass
130219
"Undefined control sequence" at beginning of any simple document
60457
Undefined reference to `sin`
30244
Is there any way to tell the compiler, inside the main file body, how to find the class?
32770
array package: problem with >{declarations} in preamble: Extra alignment tab has been changed to \cr
105528
Reference undefined in \section with amsbook
141374
'! Undefined control sequence' and '! Package inputenc error' while typesetting equations
32645
Undefined control sequence error \end{gather}
51099
\mathbb{Z} yields undefined control sequence error
147631
LaTeX Warning: There were undefined references.Why?
68686
! LaTeX Error: Command \textdegree unavailable in encoding OT1
109479
Class variables not yet supported
6731
Undefined control sequence and \chapter error
97695
Notice: Undefined index
6292
What is an undefined reference/unresolved external symbol error and how do I fix it?
106312
how to remove these errors in my tex presentation slides?
42779
Even the simplest class doesn't compile, "has not been declared
157647
mhchem ver.4 not working after update! Control sequence undefined