As a two dimensional example, number R01φ00 denotes the Green's function in a solid cylinder with angular dependence, with a type 1 (Dirichlet) boundary condition at r = a. Here letter φ denotes the angular (azimuthal) coordinate, and numbers 00 denote the type zero boundaries for angle; here no physical boundary takes the form of the periodic boundary condition. The boundary value problem for the R01φ00 Green's function is given by