Study (dates)	Number of study subjects	Type A number	Type B number	Type C number	Type D number	Type E number
German, et al.9 (1964–1974)	102	6	2	83	9	2
Sillen, et al.10 (1967–1984)	110	7	1	100	1	1
Holder, et al.11 (1973–1986)	100	2	1	85	6	6
Poenaru, et al.12 (1969–1989)	95	8	0	80	1	6
Engum, et al.3 (1971–1993)	227	29	2	178	5	13
Spitz, et al.1 (1988–1994)	410	27	4	353	9	17
Total	1,044	79 (8%)	10 (1%)	879 (84%)	31 (3%)	45 (4%)