[comp.sys.mac.hypercard] XCMDS and XFUNCTIONS, where are these documented?

rburns@teknowledge-vaxc.ARPA (Mr. Doom and Gloom) (01/20/88)

Where is the use of external functions and commands documented?  Goodman
mentions these, but not where more can be found out about the use of C
and Pascal with Hypercard.

Thanks.