Experiences using statecharts for a system requirements specification. - Nancy G. Leveson; Mats P. E. Heimdahl; Holly Hildreth; Jon Damon Reese; R. Ortega (IWSSD, 1991)

Reverse Engineering Requirements for Process-Control Software. - Holly Hildreth (ICSM, 1994)

Requirements Specification for Process-Control Systems. - Nancy G. Leveson; Mats Per Erik Heimdahl; Holly Hildreth; Jon Damon Reese (IEEE Trans. Software Eng., 1994)