Efficacy and safety of HX 110-A and HX 110-B in promoting respiratory health: protocol for an 8-week, randomized, double-blind, parallel group, placebo-controlled trial

Jung-Kyu Lee, Bumjo Oh, Hyun Woo Lee, Seo-Young Yoon, Tae Yun Park, Eun Young Heo, Deog Kyeom Kim