surface_operator  458 old_code/tumor_growth/tumor_code.h   const Tumor_surface_operator surface_operator {surface_model, u_approx};
surface_operator  459 old_code/tumor_growth/tumor_code.h   Vec_CG_Solver surface_solver {surface_operator, solverEps, solverEps};
surface_operator  537 old_code/tumor_growth/tumor_code.h     surface_operator.generate_rhs(next_surface, surface_cg_rhs);