# Undefined control sequence undetectable [closed]

I came across the following error message:

! Undefined control sequence.
{j=1 \\ j \neq k}}}^N\disp...

Pardon my ignorance.

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In the spirit of this Q&A site, please consider reviewing your existing questions and accept those answers you consider most helpful. This will both improve your current 0% accept rate, as well as make community members more willing to support and answer your questions. There is a reward for accepting answers as well. –  Werner Jan 24 '12 at 6:38
Read the FAQ entry How do I ask questions here? for guidance on voting and accepting answers. –  Werner Jan 24 '12 at 6:59
It would be helpful if, in your posting, you only included the error message and left out the (at this point) meaningless LaTeX warnings. –  Mico Jan 24 '12 at 7:11

## closed as too localized by egreg, topskip, Seamus, Joseph Wright♦Jan 24 '12 at 18:47

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You are looking for the command \substack not \substrack.

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Thak's for everyone and specially for Werner. After correction, I still have this error message: ! Undefined control sequence. l.206 ...\quad a_k > \displaystyle\sum_{{\substack {j=1 \\ j \neq k}}}^N\disp.. –  Zbigniew Jan 24 '12 at 11:42
@Labaïr If you have an error message, why not edit the question showing what you did and the error message? –  egreg Jan 24 '12 at 15:03
Now i have this message: ! LaTeX Error: Environment remarques undefined. See the LaTeX manual or LaTeX Companion for explanation. Type H <return> for immediate help. ... l.396 \begin{remarques} –  Zbigniew Jan 24 '12 at 15:04
@Labaïr: The remarques environment is not defined. But this could be a host of things. For example, if it should be a "theorem" or a regular environment. You need to post more information. –  Werner Jan 24 '12 at 15:20