Continuing 12.7B10

Revise first, second, third, and fifth examples to read:

Issues for August 1973-December 1974 also designated: volume 1, number 7-volume 2, number 12.

Volume numbering irregular: volumes 15-18 omitted, volumes 20-21 repeated .

Numbering begins each year with volume 1.

Some numbers issued in combined form.