Since the first extragalactic H2O megamaser source toward the Active Galactic Nuclei NGC 4945 was discovered, 19 sources have been found.

• 自从在活动星系核NGC 4945的视线方向上发现第一个河外 H2O超脉泽源以来,迄今为止已发现T 19个河外H2O超脉泽源。