How to write a pkgsrc Makefile for "only extract" source?

["Gueven Bay" <gueven.bay%googlemail.com@localhost>]

Hello,

I have a bunch of tar balls (or zips) - each of them at a specific
online address - for which I want to write pkgsrc Makefiles so that
each of them only get downloaded and extracted - nothing more as these
tar balls (or zips) are archives of html/xml/pdf documents -.

I read the pkgsrc guide but I cannot find a "receipt" there how to
write a Makefile only for downloading and extracting.

Can someone post a "first version" of such an Makefile, please, so
that I know how to begin?

Thank you
regards
Gueven Bay