On Sophus Lie's Fundamental Theorem
J. Hilgert, K.H. Hofmann, J. Funct. Anal. 67 (1986) 1–27.

Controllabilty of Systems on Nilpotent Lie Groups
J. Hilgert, K.H. Hofmann, J.D. Lawson, Beiträge Alg. Geom. 20 (1985) 185–190.

Semigroups in Lie Groups, Semialgebras in Lie Algebras
J. Hilgert, K.H. Hofmann, Trans. AMS 288 (1985) 481–504.

Lorentzian Cones in Real Lie Algebras
J. Hilgert, K.H. Hofmann, Monatshefte Math. 100 (1985) 183–210.

Lie Semialgebras are Real Phenomena
J. Hilgert, K.H. Hofmann, Math. Ann. 270 (1985) 97–103.

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

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