1. Prime and prime power divisibility of Catalan numbers;Alter;J. Combin. Theory Ser. A,1973
2. On the prime power divisors of the iterates of the Euler-ϕ function;Bassily;Publ. Math. Debrecen,1999
3. There are no multiply-perfect Fibonacci numbers;Broughan;Integers,2011
4. On a problem of Oppenheim concerning “Factorisatio Numerorum”;Canfield;J. Number Theory,1983
5. Note on Eulerʼs ϕ function;Carmichael;Bull. Amer. Math. Soc.,1922