Old and New on SL(2)
J. Hilgert, K.H. Hofmann, Manuscripta Math. 54 (1985) 17–52.
LibreCat: /record/51459

Lie Theory of Semigroups
J. Hilgert, K.H. Hofmann, Semigroup Forum 30 (1984) 243–251.
LibreCat: /record/51461