Applied algebra, algebraic algorithms, and error-correcting codes : 9th International Symposium, AAECC-9, New Orleans, LA, USA, October 7-11, 1991 : proceedings - Rao, T. R. N. (Thammavarapu R. N.), 1933-; Mora, Teo; Mattson, H. F. (Harold F.), 1930- (Lecture notes in computer science ;, 1991)