Petri nets

J. Peterson
"Petri Nets," ACM Computing Surveys 9(3) Sept. 1977, pp. 223-252
T. Murata
"Petri Nets: Properties, Analysis, and Applications," Proceedings of the IEEE 77(4) Apr. 1989, pp. 541-580

Axiomatic verification

C.A.R. Hoare
"An Axiomatic Basis for Computer Programming," Communications of the ACM 12(10) Oct. 1969, pp. 576-583
C.A.R. Hoare and N. Wirth
"An Axiomatic Definition of the Programming Language PASCAL," Acta Informatica 2, 1973, pp. 335-355
D. Gries
"The Science of Programming," Springer-Verlag, New York, 1981.

Functional verification

H. Mills
"The New Math of Computer Programming," Communications of the ACM 18(1), Jan. 1975, pp. 43-48

Algebraic data types

J. Guttag, E. Horowitz, and D. Musser
"Abstract Data Types and Software Validation," Communications of the ACM 21(12) Dec. 1978, pp. 1048-1064
J. Guttag
"Notes on Type Abstraction (Version 2)," IEEE Tr. on Software Eng. 6(1) Jan. 1980 pp. 13-23

Software process modeling

M. Kellner
"Software Process Modeling," Technical Review 1989, SEI, pp. 23-54