The Year Before Yesterday (1987) - an oddity which incorporates a novella from 1965 (revised), plus a short novel from 1958 (unmodified as far as I can tell) - embedded in a (new) framing narrative of four parts. In Britain (also in 1987), a revised version was published as Craken at Critical - from small publisher Kerosina Books (and later reprinted in mass-market paperback.)

The Mannerheim Symphony (I; II, III; IV) - (the framing narrative, totalling about 34 pages)

The Impossible Smile, by Jael Cracken - between I and II: serialized in 2 parts in SCIENCE FANTASY (1965, as by "Jael Cracken")

Equator + The Merdeka Hotel - between II & III, and between III & IV: two halves of Equator, serialized in 2 parts in NEW WORLDS (1958.) In America this appeared in book form as Vanguard from Alpha (half of an Ace Double.) British book versions kept the serial title.