H. W. Wilson

Mom's Memoirs:

I got a job as an “editor” with the H. W. Wilson Co in the Bronx and got fired when they found out I was pregnant.

...

I think I have already written about my brief work experience at the HW Wilson Company

Notes: Interestingly, the letter dismissing Mom doesn't mention her pregnancy. Could just of well have been them learning that she and Dad would be moving that summer.