1. M.K. Agoston, Algebraic Topology, A First Course, Marcel Dekker Inc.: New York, NY, 1976.
2. J.C. Alexander and A.I. Thaler, ?The boundary count of digital pictures,? J. Assoc. Computing Machinery, Vol. 18, No. 1, pp. 105?112, 1971.
3. G. Burde and W. Zieschang, Knots, W. de Gruyter, New York, NY, 1985.
4. R.H. Crowell and R.H. Fox, Introduction to Knot Theory, Blaisdell Publishing Company: Boston, 1963.
5. P.J. Giblin, Graphs, Surfaces and Homology, 2nd Ed., Chapman and Hall: London, 1987.