X11 include files..

[I Rattan <ratta1i@cps.cmich.edu>]

I am running Sidux and trying to compile plan9port.
I see the error messages:

...
x11-inc.h:13:22: error: X11/Xlib.h: No such file or directory
x11-inc.h:14:23: error: X11/Xatom.h: No such file or directory
x11-inc.h:15:23: error: X11/Xutil.h: No such file or directory
x11-inc.h:16:24: error: X11/keysym.h: No such file or directory
x11-inc.h:17:28: error: X11/IntrinsicP.h: No such file or directory
x11-inc.h:18:28: error: X11/StringDefs.h: No such file or directory
...

what debian package may include these header files?
-ishwar