Hilgert, J. (1991). Group Theoretical Aspects of Gödels Model. In J. Hilgert (Ed.), Jahrbuch der Gödel Gesellschaft.
LibreCat: /record/51483

Hilgert, J. (1991). Infinitesimally Generated Subsemigroups of Motion Groups. Rocky Mount. J. Math., 21, 865–878.
LibreCat: /record/51444

Hilgert, J., &; Neeb, K.-H. (Eds.). (1991). Lie-Gruppen und Lie-Algebren. Vieweg Verlag.
LibreCat: /record/51497

Hilgert, J. (1991). Onishchik, A.L., und E.B. Vinberg. Lie Groups and Algebraic Groups (Springer, New York, 1990). In Zentralblatt (Vol. 722).
LibreCat: /record/51586

Rösler, M. (1991). On optimal linear mean estimators for weakly stationary stochastic processes. Orthogonal Polynomials and Their Applications (Erice, 1990), 373–378.
LibreCat: /record/40656

Hilgert, J. (1990). Applications of Lie Semigroups in Analysis. In K. H. Hofmann &; et al. (Eds.), The Analytical and Topological Theory of Semigroups. De Gruyter.
LibreCat: /record/51484

Hilgert, J., &; Hofmann, K. H. (1990). On the Causal Structure of Homogeneous Manifolds. Math. Scand., 67, 119–144.
LibreCat: /record/51446

Dellnitz, M., &; Werner, B. (1989). Computational methods for bifurcation problems with symmetries—with special attention to steady state and Hopf bifurcation points. Journal of Computational and Applied Mathematics, 97–123.https://doi.org/10.1016/0377-0427(89)90150-7 
LibreCat: /record/16682
DOI: 10.1016/0377-0427(89)90150-7

Hilgert, J., &; Hofmann, K. H. (1989). Compactly Embedded Cartan Algebras and Invariant Cones in Lie Algebras. Advances Math., 75, 168–201.
LibreCat: /record/51448

Hilgert, J. (1989). A Note on Howe’s Oscillator Semigroup. Ann. Inst. Fourier, 39, 663–688.
LibreCat: /record/51447