The operators under consideration will be formed from nine basic first order operators. These will, in their turn, be formed by combining in several ways one of their number, an undefined operator of 'derivation'.
Proceedings of the Iowa Academy of Science
©1941 Iowa Academy of Science, Inc.
"On the Independence of Operators on a Lattice,"
Proceedings of the Iowa Academy of Science, 48(1), 301-304.
Available at: https://scholarworks.uni.edu/pias/vol48/iss1/74