> I shall not sleep until I figure this out!<p>Number 9 was printed after number 17 - <a href="https://www.librarything.com/nseries/81668/Computer-Monographs" rel="nofollow">https://www.librarything.com/nseries/81668/Computer-Monograp...</a> (Click on publication) 11 might have been a place holder that didn't make it.<p>You can try searching the editor on the internet archive - <a href="https://archive.org/details/inlibrary?tab=collection&query=%22Stanley+Gill%22&sin=TXT" rel="nofollow">https://archive.org/details/inlibrary?tab=collection&query=%...</a> or the publishers "London, Macdonald and Co.; New York, American Elsevier" or in "The British National Bibliography cumulated index, 1968-1970" <a href="https://archive.org/details/britishnationalb0000unse_x4v2/page/378/mode/2up?q=%22Computer+monographs%22" rel="nofollow">https://archive.org/details/britishnationalb0000unse_x4v2/pa...</a> (The "who is related to whom" might be a typo)