1. Articles inConcepts and Applications of Molecular Similarity, eds. M.A. Johnson and G.M. Maggiora (Wiley, New York, 1990).
2. P.G. Mezey,Shape in Chemistry (VCH, New York, 1993).
3. R.T. Sanderson,Chemical Periodicity (Reinhold, New York, 1960).
4. G. Birkhoff,Lattice Theory (Am Math. Soc., Providence, RI, 1948).
5. P. Crawley and R.P. Dilworth,Algebraic Theory of Lattices (Prentice-Hall, Englewood Cliffs, New Jersey, 1973).