Volkan Gökbulut, et al. “Parenteral Methotrexate Is Efficient in the Treatment of Azathioprine Refractory Crohn’s Disease”. Turkish Journal of Gastroenterology, vol. 33, no. 2, Feb. 2022, pp. 111-8, https://tjg.avesjournals.com/index.php/tjg/article/view/4188.