“…This approach was successfully used before the isogeometric development. The works of Zieniuk [21], Zieniuk and Boltuc [22], and Zieniuk and Szerszeń [23], among others, proposed the concept of parametric integral equation system (PIES) for accurate representation of boundary geometry. In these works, the boundary geometry was described as a parametric function that was included in the PIES kernels, rather than in the boundary integral as is done in standard BEM.…”