35F15 Boundary value problems for linear first-order equations

35F16 Initial-boundary value problems for linear first-order equations

35F25 Initial value problems for nonlinear first-order equations

35F30 Boundary value problems for nonlinear first-order equations

35F31 Initial-boundary value problems for nonlinear first-order  equations

35F40 Initial value problems for linear first-order systems

35F45 Boundary value problems for linear first-order systems

35F46 Initial-boundary value problems for linear first-order systems

35F55 Initial value problems for nonlinear first-order systems

35F60 Boundary value problems for nonlinear first-order systems

35F61 Initial-boundary value problems for nonlinear first-order systems

35F99 None of the above, but in this section

35Gxx General higher-order equations and systems

35G10  Initial value problems for linear higher-order equations

35G15 Boundary value problems for linear higher-order equations

35G16 Initial-boundary value problems for linear higher-order equations

35G25 Initial value problems for nonlinear higher-order equations

35G30 Boundary value problems for nonlinear higher-order equations

35G31 Initial-boundary value problems for nonlinear higher-order equations

35G40 Initial value problems for linear higher-order systems

35G45 Boundary value problems for linear higher-order systems

35G46 Initial-boundary value problems for linear higher-order systems

35G55 Initial value problems for nonlinear higher-order systems

35G60 Boundary value problems for nonlinear higher-order systems

35G61 Initial-boundary value problems for nonlinear higher-order systems

35G99 None of the above, but in this section

35Hxx Close-to-elliptic equations and systems

35H99 None of the above, but in this section

35Jxx Elliptic equations and systems [See also <a href="#code:58J10">58J10</a>, <a href="#code:58J20">58J20</a>]

35J05 Laplacian operator, reduced wave equation (Helmholtz equation), Poisson equation [See also <a href="#code:31Axx">31Axx</a>, <a href="#code:31Bxx">31Bxx</a>]