Kumar, I. et al. 2017. Retrograde gastroesophageal intussusception: an exceedingly rare complication of Heller myotomy in a patient with achalasia cardia. Turkish Journal of Gastroenterology. 28, 4 (Jan. 2017), 316–318. DOI:https://doi.org/10.5152/tjg.2017.17057.