# Reference request: Proof of Lemma 3.3 in Linear and Quasi-linear Equations of Parabolic Type

The following lemma in Linear and Quasi-linear Equations of Parabolic Type by Nina Uraltseva, Olga Ladyzhenskaya, and Vsevolod A. Solonnikov.

Lemma 3.3 Let $$\Omega\subset\mathbb{R}^n$$ satisfy a cone condition. Then for any function $$u(x,t)$$ from $$W^{2l,l}_q(Q_T)$$ with integral $$l$$ the inequality

$$||D_t^rD_x^su||_{p,Q_T} \leq c_3\delta^{2l-2r-s-(1/q-1/p)(n+2)} \langle\langle u\rangle\rangle_{q,Q_T}^{(2l)} + c_4\delta^{-[2r-s+(1/q-1/p)(n+2)]}||u||_{q,Q_T}$$

is valid under the conditions $$p\geq q$$, $$2l-2r-s-(1/q-1/p)(n+2)\geq 0$$. Then constant $$\delta$$ here must satisfy the condition

$$0<\delta \leq \min\{d;\sqrt{T}\}$$

and the constants $$c_3,c_4$$ depend on $$l,r,s,n,q$$.

See Lemma 3.3, p. 80 in Linear and Quasi-linear Equations of Parabolic Type by Nina Uraltseva, Olga Ladyzhenskaya, and Vsevolod A. Solonnikov for some details.

QUESTIONS: In the book the authors cited a paper of V. A. Solonnikov for the proof of this lemma. However, I cannot find the Solonnikov's paper. So does anyone have reference to the proof of Lemma 3.3 above?

I believe this is well-known lemma. So many experts in the PDEs field must know how to prove it. Thanks.

• I believe proof of Lemma 3.3 is in V. A. Solonnikov – A priori estimates for second-order parabolic equations (ams.org/books/trans2/065). However I cannot download it. Maybe somone so nice to help me. Thanks a lot. – Ngu Dec 21 '18 at 11:56