1. ‘Second CCIR computer-based interim method for estimating skywave field strength and transmission loss at frequencies between 2 and 30 MHz’, CCIR Supplement, Rep. 252-2, , Kyoto, 1978
2. Pigott, W.R., Rawer, K., URSI handbook of ionogram interpretation and reduction, 2nd ed., Warsaw 1972),Rep. UAG-23A