These four pamphlets were issued by T-K Graphics between 1974 and 1977. The covers are printed in black on colored paper and feature typefaces that all seem to stem from the catalogs of VGC, ITC and Letraset.
Fanlore has a page about this publisher:
T-K Graphics was a distributor/retailer of pro books, but it is more well-known for publishing fan-created chapbooks and other amateur zines.
It was based in Baltimore, Maryland was founded in the early 1970s, perhaps earlier.
Via jell-o biafra says, a great (but sadly dormant) Tumblr for all things pulp, pop and underground.