Both a fractional and integer quantum effect exist.
References
Chakraborty, T. and Pietiläinen, P. The Fractional Quantum Hall Effect: A Survey of the Incompressible Quantum Fluid Including the Quantum Hall Effect, 2nd ed. New York: Springer-Verlag, 1995.
DasSarma, S. Perspectives in Quantum Hall Effects: Novel Quantum Liquids in Low-Dimensional Semiconductor Structures. New York: Wiley, 1996.
Janssen, M.; Vieweg, O.; Fastenrath, U.; and Hajdu, J. Introduction to the Theory of the Integer Quantum Hall Effect. New York: VCH, 1994.
Prange, R. E. and Girvin, S. M. The Quantum Hall Effect, 2nd ed. New York: Springer-Verlag, 1990.
Weisstein, E. W. "Books about Quantum Hall Effect." http://www.ericweisstein.com/encyclopedias/books/QuantumHallEffect.html.
