Note:
Quote (verbatim; underscore represents a linked cross-references):
All his sf novels are for a sophisticated Young Adult readership; the most important of them is the Mars sequence comprising The Angry Planet (1945) and its sequel, SOS from Mars (1954; vt The Red Journey Back 1954), both presented as Cross's transcription of manuscripts composed "by Stephen MacFarlane" [see Checklist for full subtitles], and encompassing the first three expeditions to Mars , which discover the vegetable life there to have suffered a Manichaean Evolution into alternative races.
--SFE3, biographical entry by John Clute
That Encyclopedia of SF entry is linked here for convenient reference to the full titles as interpreted by the editors. There two other books are listed "as by Stephen MacFarlane" but these are listed as "under his own name".