1991
January January; 128 (1): 1 - 640	February February; 128 (2): 643 - 1206	March March; 128 (3): 1209 - 1686
April April; 128 (4): 1687 - 2206	May May; 128 (5): 2209 - 2668	June June; 128 (6): 2671 - 3337
July July; 129 (1): 1 - 574	August August; 129 (2): 575 - 1136	September September; 129 (3): 1137 - 1686
October October; 129 (4): 1687 - 2269	November November; 129 (5): 2271 - 2805	December December; 129 (6): 2807 - 3456