Contractions of the actions of reductive algebraic groups in arbitrary characteristic. Frank D. Grosshans — 1992 Inventiones mathematicae
Hilbert's Fourteenth Problem for Non-Reductive Groups. Frank D. Grosshans — 1986 Mathematische Zeitschrift
Separeted orbits for certain non-reductive subgroups. Frank D. Grosshans — 1988 Manuscripta mathematica
Constructive geometric invariant theory for certain nonreductive groups Frank D. Grosshans — 1990 Banach Center Publications