1991
January January; 173 (1): 1 - 416 January; 173 (2): 417 - i4	February February; 173 (3): 937 - 1366 February; 173 (4): 1367 - 1568	March March; 173 (5): 1569 - 1837 March; 173 (6): 1839 - 2145
April April; 173 (7): 2147 - 2409 April; 173 (8): 2411 - 2731	May May; 173 (10): 3035 - 3269 May; 173 (9): 2733 - 3034	June June; 173 (11): 3271 - 3608 June; 173 (12): 3609 - 3933
July July; 173 (13): 3935 - 4245 July; 173 (14): 4247 - 4549	August August; 173 (15): 4551 - 4908 August; 173 (16): 4909 - 5246	September September; 173 (17): 5247 - 5596 September; 173 (18): 5597 - 5933
October October; 173 (19): 5935 - 6311 October; 173 (20): 6313 - 6649	November November; 173 (21): 6651 - 7063 November; 173 (22): 7065 - 7404	December December; 173 (23): 7405 - 7740 December; 173 (24): 7741 - 8014