 Besides a p-refinement, the element can be subdivided in space (as in h-adaptivity), but there are many combinations for the polynomial degrees on the subelements.This is illustrated in the figure on the right.For example, if a triangular or quadrilateral element is subdivided into four subelements where the polynomial degrees are allowed to vary by at most two, then this yields 3^4 = 81 refinement candidates (not considering polynomially anisotropic candidates).