Source: https://www.researchgate.net/profile/Chaib-Rachid/publication/269095553_Modelisation_de_la_Fiabilite_d'un_Systeme_Mecanique_a_redondance/links/547f48790cf250f1edbdc06a/Modelisation-de-la-Fiabilite-dun-Systeme-Mecanique-a-redondance.pdf