Problem definition# Operators on unknowns/kernels Available differential operators The DifferentialOperator class The Operand class The OperatorOnUnknown class The OperatorOnUnknowns class The LcOperatorOnUnknown class The LcOperatorOnUnknowns class The OperatorOnKernel class The KernelOperatorOnUnknowns class The TensorKernel class Integration methods The best rules per shape and order The IntegrationMethod, SingleIM, DoubleIM classes The QuadratureIM class The ProductIM class The Quadrature, QuadratureRule classes Integration methods for singular kernels H-matrices Cluster tree Approximate matrix