Next Tuesday, May 10th between 5am and 7am the AMS website will be undergoing routine maintenance and may be unavailable during those hours.
ISSN 1088-9485(online) ISSN 0273-0979(print)
Research problems: Problems concerning semigroups
A. D. Wallace
Bull. Amer. Math. Soc. 68 (1962), 447-448
Full-text PDF Free Access