1. Boynton, P.E., Stokes, R.A., Wilkinson, D.T. 1968, Phys.Rev.Lett. 21, 462.
2. Dall’oglio, G., Fonti, S., Melchiorri, B., Melchiorri, F., Natale, V., Lombardirii, P., Trivero, P., Sivertson, S. 1976, Phys.Rev.D, 13, 1187.
3. Gush, H.P. 1981, Phys.Rev.Lett. 47, 745.
4. Kalckar, J., Ulfbeck, O., Nilsson, N.R. 1980 (Eds.) The Universe at Large Redshifts, Physica Scripta 21, No. 5.
5. Martin, D.H. 1982, Ch. 2 of Infrared and Millimetre Waves, Vol. 6, Ed. K.J. Button, Academic Press.