Source: http://di.univ-blida.dz:8080/jspui/bitstream/123456789/4135/1/Serir%20kamilia%20%28%20Finition%20des%20pi%C3%A8ces%20complexes%20par%20la%20strat%C3%A9gie%27%27%20Plans%20parall%C3%A8les%27%27%29.pdf