1991
January January; 81 (1): 1 - 45	February February; 81 (2): 57 - 102	March March; 81 (3): 112 - 161
April April; 81 (4): 167 - 223	May May; 81 (5): 231 - 275	June June; 81 (6): 281 - 329
July July; 81 (7): 338 - 388	August August; 81 (8): 399 - 454	September September; 81 (9): 463 - 509
October October; 81 (10): 519 - 568	November November; 81 (11): 575 - 624	December December; 81 (12): 631 - 665