1.Charging for upgrades provides a continual source of revenue for your business.
发布重大升级版时收费给你的生意提供了一个持续的收入来源。
2.Her daughter was a continual source of delight to her.
她的女儿是她无限快乐的源泉。
3.But more important, the pan-African student body is a continual source of strength, pride and commitment to Africa.
更重要的是，泛非主义的学生，是非洲强大，自豪和振兴的不竭源泉。
4.The continual source of our strength was our mutual trust and respect.
相互信任和尊重是我们俩永不枯竭的力量源泉。