Ahmad, Khawaja Khurshid, Asim Shaukat, Muhammad Ali, Yasser Amin, Tahir Qadeer, and Sarfraz Ahmad. 2016. “Is Secondary Achalasia a Reality? Primary Versus Secondary Achalasia: Role of Barium Swallow”. Annals of King Edward Medical University 9 (4). https://doi.org/10.21649/akemu.v9i4.1375.