1. American Association of State Highway and Transportation Officials (AASHTO) M320 (2002) "Standard Specification for Performance-Graded Asphalt Binder " Standard Specifications for Transportation Materials and Methods of Sampling and Testing Part 1B Washington D.C.
2. Bahia H. (1991) "Low-Temperature Isothermal Physical Hardening of Asphalt Cements" Ph.D. thesis Pennsylvania State University University Park PA.