1. Nikuradse, J. , 1933,Laws of Flow in Rough Pipe, VDI, Forchungsheft No. 361, English translation NACA T.M. 1292, 1950.
2. TURBULENT FLOW IN PIPES, WITH PARTICULAR REFERENCE TO THE TRANSITION REGION BETWEEN THE SMOOTH AND ROUGH PIPE LAWS.
3. Sletfjerding, E. , 1999, “Friction Factor in Smooth and Rough Gas Pipelines,” Dr.-Ing. thesis, Norwegian University of Science and Technology, Trondheim.
4. Friction Factor Directly From Roughness Measurements
5. TECHNICAL NOTE. NEW FORMS OF EQUATIONS FOR THE CORRELATION OF PIPE RESISTANCE DATA.