1. National Bureau of Standards Applied Mathematics Series,1964
2. R.A. Adams, Sobolev Spaces. Academic Press, New York, 1975.
3. M.S. Ashbaugh and R.D. Benguria, On Rayleigh’s conjecture for the clamped plate and its generalization to three dimensions. Duke Math. J. 78 (1995), 1–17.
4. M.S. Ashbaugh and R.S. Laugesen, Fundamental tones and buckling loads of clamped plates. Ann. Scuola Norm. Sup. Pisa CI. Sci., Ser. IV. To appear.
5. R. Askey, editor, Gabor Szegő: Collected Papers, Volume 3: 1945–1972, Birkhäuser, Boston, 1982.