Ilan E. Timor-Tritsch, Ana Monteagudo, Edgar O. Mandeville, David B. Peisner, Guido Parra Anaya, Exenia C. Pirrone,
Successful management of viable cervical pregnancy by local injection of methotrexate guided by transvaginal ultrasonography American Journal of Obstetrics and Gynecology. ,vol. 170, pp. 737- 739 ,(1994) ,
10.1016/S0002-9378(94)70273-X