1. Sobolev spaces;Adams,1975
2. P. Auscher, A. McIntosh, P. Tchamitchian, Heat kernels of second order complex elliptic operators and applications, J. Funct. Anal.
3. Sharp bounds on heat kernels of higher order uniformly elliptic operators;Barbatis;J. Operator Theory,1996
4. G. Barbatis, Sharp heat kernel bounds and Finsler-type metrics, Quart. J. Math.
5. Spectral asymptotics of non-smooth elliptic operators I;Birman;Trans. Moscow Math. Soc.,1972