1. An Introduction to the theory of Numbers;Hardy,1960
2. More on panarithmic numbers;Heyworth;New Zealand Math. Mag.,1980
3. Résultats et conjectures sur les nombres pratiques;Margenstern;C. R. Acad. Sci. Sér. I,1984
4. Egyptian fractions via Greek number theory;Robinson;New Zealand Math. Mag.,1979
5. Approximate formulas for some functions of prime numbers;Rosser;Illinois J Math.,1962