1. B.N. Ellison, P.L. Schaffer, W. Schaal, D. Vail and R.N. Miller, Internat. J. of Infrared and Millimeter Waves10, 937 (1989).
2. C.K. Walker, J.W. Kooi, M. Chan, H.G. LeDuc, P.L. Schaffer, J.E. Carlstrom and T.G. Phillips,Proc. 3rd Internat. Symp. on Space Terahertz Technology, p. 266, University of Michigan, MI (1992).
3. J. Zmuidzinas and H.G. LeDuc, IEEE Trans. Microwave Theory and Techn.40, 1797 (1992).
4. J. Mees, G. DeLange, A. Skalare, C.E. Honingh, M.M.T.M. Dierichs, H. Kuipers, R.A. Panhuyzen, H. van de Stadt, M.W.M. de Graauw, and T.M. Klapwijk,Proc. 18th Internat. Conf. on Infrared and Millimeter Waves, p. 280, Colchester, U.K. (1993).
5. J.R. Tucker, Appl. Phys. Lett.36, 477 (1980).