B.30 Undefined control sequence

LaTeX doesn't understand the command you have used.

Check to see if you have misspelt the command name (remember that all LaTeX command names are case-sensitive.)
You will get this error if you do, say,
✘ This is a simple \Latex\␣document
instead of
✔ This is a simple \LaTeX\␣document
Check that you have remembered the space when typing \␣ (backslash space). For example, this error will occur if you do, say,
✘ This is a \LaTeX\sample document.
instead of
✔ This is a \LaTeX\␣sample document
If you are using a command that is defined in a package make sure you have included the package using \usepackage.
Check that your command name hasn't run into the next piece of text. For example, you can do
man\oe{}uvre
or
man\oe uvre
or (not recommended)
man{\oe}uvre
but not
✘ man\oeuvre
Check if you have used a backslash instead of a forward slash as a directory divider. (Remember that when using LaTeX under Windows, you need to use a forward slash (/) as the directory divider, as a backslash would be interpreted as a command.)
For example, suppose you have a file called shapes.pdf in a subdirectory called pictures, then you would get an error if you did
✘ \includegraphics{pictures\shapes}
instead of
✔ \includegraphics{pictures/shapes}

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