Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A centennial of the Zaremba--Hopf--Oleinik Lemma   We discuss the problem how "bad" may be lower-order coefficients in elliptic
and parabolic second order equations to ensure the Hopf--Oleinik Lemma for
solutions to hold true. We also touch the gradient estimates for solutions at
the boundary.

9
The categories of this paper are: nlin
8
The categories of this paper are: hep-ex
4
The categories of this paper are: cond-mat
26
The categories of this paper are: bayes-an
7
The categories of this paper are: hep-th
19
The categories of this paper are: eess
22
The categories of this paper are: chao-dyn
27
The categories of this paper are: comp-gas
10
The categories of this paper are: q-bio
11
The categories of this paper are: hep-lat
1
The categories of this paper are: cs
18
The categories of this paper are: econ
20
The categories of this paper are: acc-phys
5
The categories of this paper are: gr-qc
36
The categories of this paper are: cmp-lg
14
The categories of this paper are: math-ph