2001, Gian-Carlo Rota, What is invariant theory, really?, H. Crapo, D. Senato (editors), Algebraic Combinatorics and Computer Science: A Tribute to Gian-Carlo Rota, Springer, page 41,
For alinear algebraic group and a regular representation of , the basic problem of invariant theory is to describe the -invariant elements of the -fold tensor product for all .
Used other than figuratively or idiomatically: seeinvariant, theory.