1. F.G. Kelly et al., Spacecraft altitude detector utilizing solar sensors and summation of predetermined signals derived therefrom, US Patent 3.493.765.
2. G.A. Zerlaut et al., Solar tracking device, US Patent 4.031.384.
3. G.L. Haywood et al., Solar collectors and drive circuitry control means, US Patent 4.082.947.
4. H.U. Rauth, A. Dress, R. Pruschek, T. Weidele, Annually generated electricity of one and two axes solar tracking systems, Proc. 13th European PV Solar Energy Conf., Nice, 23–27 October 1995, pp. 1015–1018.
5. Grid connected PV plants: field experiences in Germany a pursuit of higher solar energy collection efficiency;Imamura;Solar Energy Mater. Solar Cells,1994