Correction:
Andrew S. Tanenbaum published Minix in “Operating Systems”, Douglas Comer, Xinu, a similar idea. The way things work is most of the work creating both was done by graduate students under their direction.
Correct. I have Tanenbaum's original book on my shelf as well as Doug Comer's work. Comer was more focused on networking. Tanenbaum had a broader approach.