Singh, J; Prabhu, T. P
(Springer, 1985-11)
Daily calcium plage areas for the period 1951-1981 (which include the solar cycle 19 and 20) have been used to derive the rotation period of the sun at latitude belts 10-15 deg N, 15-20 deg N, 10-15 deg S, and 15-20 deg ...