1. Ehrich, F. F., ?Subharmonic vibration of motors in bearing clearance?. ASME paper 66-MD-1, 1966.
2. Day, W. B., ?Nonlinear rotordynamics analysis?, NASA report CR 171425, 1985.
3. Neilson, R. D. and Barr, A. D. S., ?Spectral features of the response of a rigid rotor mounted on discontinuously nonlinear supports?, 7th World Congress on the Theory of Machines and Mechanics, Seville, 1984, 1799?1803.
4. Bently, D. E., ?Forced subrotative speed dynamic action of rotating machinery?, ASME paper 74-PET-16, 1974.
5. Childs, D. W., ?Fractional frequency rotor motion due to nonsymmetric clearance effects?, ASME J. of Engl. Power 104, 1982, 533?541.