D.  van Halsema, Snoeij, P., Calkoen, C. J., Oost, W. A., Vogelzang, J., and Jähne, B., ?Modulation of the microwave backscatter by long gravity waves as measured in a very large wind/wave flume?, in Proc. IGARSS '91, 1991, vol. 3, p. 1293--1296.