Bonn — For a second time within a 24-hour period, an American Army building in West Germany was attacked. No one was injured in either incident. The two attacks occurred in Frankfurt and Giessen March 29 and 30, Monitor correspondent Elizabeth Pond reports. A little-known group linked with the Baader-Meinhof terrorist band and calling itself "Anti-af" claimed responsibility. It associated its attacks with a warning about further violence if any Baader-Meinhof members now in prison should die in a hunger strike. The hunger strike was begun to try to secure less isolated prison conditions for t he strikers.