Can't compile an SDL program under Linux

What do you need to link an SDL program to in Linux? I have a program that works under Windows, and I want to compile it under Linux. I get several hundred linker errors, one of which is

Code:

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In function `SDL_XineramaQueryScreens':
: undefined reference to `_XFlush'

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There are also function like `dlopen', `XmissingExtension', and `sem_init'.

Which librar[y|ies] [is|are] th[is|ese] in?

Make sure you have the X development libraries installed.

I know, I was wondering where those were. I figured it out -- /usr/lib/libxmms.so.1.3.1 on my computer.

Thanks.