Tcl and the Tk Toolkit. Addison-Wesley Company Inc (ISBN 0-201-63337-X). The Tcl/Tk toolkit home page is http://tcl.activestate.com. The primary download area is http://prdownloads.sourceforge.net/tcl/.
Practical Programming in Tcl and Tk. Prentice Hall (ISBN 0-13-616830-2).