RT Journal Article SR Electronic T1 What is causing the ‘long-hauler’ phenomenon after COVID-19? JF Cleveland Clinic Journal of Medicine JO Cleve Clin J Med FD Cleveland Clinic SP 273 OP 278 DO 10.3949/ccjm.88a.21009 VO 88 IS 5 A1 Leonard H. Sigal YR 2021 UL http://www.ccjm.org/content/88/5/273.abstract AB