Trivial extensions of Abelian categories /

by Fossum, Robert M., Fossum, Robert M., Griffith, Phillip 1938-, Reiten, Idun 1942-
Published 1964

Exterior differential systems and Euler-Lagrange partial differential equations /

by Bryant, Robert L., Bryant, Robert L., Griffith, Phillip 1938-, Grossman, Daniel Andrew 1974-
Published 2003