Tobacco spending and the perceived cost of tobacco among smokers living with HIV and receiving treatment at outpatient clinics in Viet Nam: A mixed methods study - Gloria Guevara Alvarez; Thanh Hoang; Reet Kapur; Claire Nguyen; Mari Armstrong-Hough; Trang Nguyen; Nam Nguyen; Hoang Van Minh; Donna Shelley (PLoS ONE, 2025)