1. There are Infinitely Many Carmichael Numbers
2. L. E. Dickson,History of the Theory of Numbers, Vol.I,Divisibility and Primality, Chelsea Publishing,New York,1966.
3. P. van Emde Boas,D. Kruyswijk,A combinatorial problem on finite Abelian groups,Math. Centrum Amsterdam Afd. Zuivere Wisk.1967(1969) ZW-009.