fourth sphere books printing according to indica publishing history:
this depends on the two 1971 variants being alternative bind-ups of a single 1971 sphere books printing, and not separate printings.
cover art by bruce pennington
cover price 65p,
224pp. including titles, indica etc, author's introduction (1970) end pp. advertising
''sphere science fiction classic'' no longer on front cover in chief.
all sphere books p/b printings liable to include van vogt's introduction.