“…Other authors have also dealt with the WTLS problem (e.g. Shen et al, 2011;Tong et al, 2011;Mahboub, 2012;Xu et al 2012Xu et al , 2014Fang, 2013Fang, , 2014aFang, , 2014bFang, , 2014cFang, , 2015Fang and Wu, 2015;Hu et al 2015), all of them relying on the fundamental paper by Schafrin and Wieser (2008).…”