> 35-XX Partial differential equations > 35GXX General higher-order equations and systems

35G05 General theory of linear higher-order PDE	35G10 Initial value problems for linear higher-order PDE, linear evolution equations	35G15 Boundary value problems for linear higher-order PDE
35G20 General theory of nonlinear higher-order PDE	35G25 Initial value problems for nonlinear higher-order PDE, nonlinear evolution equations	35G30 Boundary value problems for nonlinear higher-order PDE
35G99 None of the above, but in this section

35GXX General higher-order equations and systems