For the 12 or 15 people in the world who know or care the Canadian publisher Export Publishing Enterprises Ltd. has a well deserved reputation for editorial sloppiness. Here's an example.
Danny Halperin was a Canadian writer of pulp literature in the 1940s and, at least, early 1950s. He was published under a number of pseudonyms including one used on four Export books - Neil H. Perrin. But Export had trouble with his first name.
The first book is News Stand Library (NSL) 66 - This Was Joanna. It's "Niel" on the front cover and title page, "Neil" on the spine and back cover. The book was published in Export's American series as 10A with the same title but a different pseudonym, Grant R. Brooks.
The second book is NSL 75 - Introducing Mr. Phreet. It's "Niel" on the front cover, "Neil" on the back cover and title page with no first name on the spine.
The third book is NSL 89 - Death be My Destiny. It's "Neil" on the front cover, spine, back cover and title page.
The fourth book is NSL 21A - The Door Between. It's "Neil" on the front cover, spine, back cover and title page.
The final tally is "Neil" 12 times, "Niel" three times.
Interestingly, Perrin/Halperin is the subject of an article (Michelle Denise Smith, "Guns, Lies, and Ice: The Canadian Pulp Magazine Industry and the Crime Fiction of Raymond Chandler and Niel [sic] Perrin", Dime Novel Roundup, Vol. 74, No. 1, February 2005) contrasting him with, of all people, Raymond Chandler. The focus is on their pulp work so none of Export's novels are mentioned. Oddly "Niel" is used in the title and throughout the article even though a cover of the Canadian pulp World Wide Detective is reproduced showing an article by "Neil Perrin". The article doesn't mention that Perrin is a pseudonym.
NSL 66 - September 1949
NSL 75 - October 1949
NSL 89 - January 1950
NSL 21A - February 1950