cv.complex variables - Bernstein inequality for multivariate polynomial

Tung, S. H. Bernstein's theorem for the polydisc. Proc. Amer. Math. Soc. 85 (1982), no. 1, 73--76. MR0647901 (83h:32017)

(from MR review): Let $P(z)$ be a polynomial of degree $N$ in $z=(z_1,cdots,z_m)$; suppose that $|P(z)|leq 1$ for $zin U^m$; then $|DP(z)|leq N$ for $zin U^m$ where $|DP(z)|^2=sum_{i=1}^m|partial P/partial z_i|^2$.

Here $U^m$ is the polydisc. Same author proved Bernstein-type inequality for the ball,
Tung, S. H. Extension of Bernšteĭn's theorem. Proc. Amer. Math. Soc. 83 (1981), no. 1, 103--106. MR0619992 (82k:32013)