The actual appearance of P-I has been as follows:

VOLUME	NUMBERS	WHOLE NO.	YEAR
1	1-4	1-4	July 1962-April 1963
2	1-4	5-8	July 1963-April 1964
3	1-4	9-12	July 1964-April 1965
4	1-3	13-15	July 1965-Jan. 1966
5	1-3	16-18	July 1968-March 1969
	Vol. 5 was reprinted in 1982; all numbers bound in one cover. The reprint has the ads deleted but photographs omitted from original text are included.
6	1-4	19-22	Jan. 1970-Oct. 1970
7	1-4	23-26	July 1971-April 1972
8	1-4	27-30	July 1972-April 1973
9	1-4	31-34	July 1973-April 1974
10	1-4	35-38	July 1974-April 1975
11	1-4	39-42	July 1975-April 1976
12	1-4	43-46	July 1976-April 1977
13	1-4	47-50	July 1977-April 1978
14	1-4	51-54	July 1978-April 1979
15	1-4	55-58	July 1979-April 1980
	Cover of Vol. 15 No.3 has Vol. 15 No.2; No. 4 was actually released January 1981
16	1-4	59-62	Jan. 1981-Oct. 1981
17	1-4	63-66	Jan. 1982-Oct. 1982
18	1-4	67-70	Jan. 1983-Oct. 1983
19	1-4	71-74	Jan. 1984-Oct. 1984
	Beginning with Vol. 19, only the whole number appears on the covers.
20	1-4	75-78	Jan. 1985-Oct. 1985
21	1-4	79-82	Jan. 1986-Oct. 1986
22	1-4	82-86	January 1987-October 1987
23	1-4	87-90	January 1988-October 1988
24	1-4	91-94	January 1989-October 1989
25	1-4	95-98	January 1990-October 1990
26	1-4	99-102	Jan./Apr. 1991 - Oct./Dec. 1991
27	1-4	103-106	Jan./Mar. 1992 - Oct./Dec. 1992
	Beginning with volume 28 the journal went to a wider page format
28	1-4	107-110	Jan./Mar. 1993 - Oct./Dec. 1993
	Cover of whole no. 108 has whole no. 107 (again)
29	1-4	111-114	Jan./Mar. 1994 - Oct./Dec. 1994
30	1-4	115-118	Jan./Mar. 1995 - Oct./Dec. 1995
31	1-4	119-122	Jan./Mar. 1996 - Oct./Dec. 1996
	Cover of whole no. 121 has whole no. 120 (again)
32	1-4	123-126	Jan./Mar. 1997 - Oct./Dec. 1997