1. AHO, A.V., DESIGN ANAL COMPUTER: CH10 (1974).
2. BARBER, M.N., RANDOM RESTRICTED WA: CH7 (1970).
3. BORCHARDT, C.W., J REINE ANGEWANDTE M 57: 111 (1860).
4. BOYER, C.B., HISTORY MATHEMATICS: 555 (1968).
5. BUCHI, J.R., Z MATH LOGIK GRUNDLA 6: 66 (1960).