W. Borho: Befreundete Zahlen. In 1847 Borho, 5-38. 11556 Graeme Cohen/Herman te Riele: On phi-amicable pairs. Math. Comp. 67 (1998), 399-411. Kevin Hare: More on the total number of prime factors of an odd perfect number. Math. Computation ... (2004), ... An odd perfect number, if it exists, has at least 47 (not necessarily distinct) prime factors. 18974 Pace Nielsen: Odd perfect numbers have at least nine distinct prime factors. Math. Comp. ... (2007), 18p. 8334 Herman te Riele: A new method for finding amicable pairs. CWI Report NM-R9512 (1995), 20p. John Voight: On the nonexistence of odd perfect numbers. MASS Selecta AMS 2003, 293-300. S. Yan: Perfect, amicable and sociable numbers. A computational approach. World Scientific 1996, 340p. 9-810-22847-3. Pds. 47.