Complex sentence: Volumes 1-7 (1975--1981) were published exclusively in microfiche format; volumes 8-14 (1982--1989) were published in a combination of microfiche and print formats.
Split into simpler sentences: Volumes 1-7 (1975--1981) were published exclusively in microfiche format; there was no print version. Volumes 8-14 (1982--1989) were published in a combination of microfiche and print formats.