RT Journal Article SR Electronic T1 Risk/caution of vitamin D insufficiency for quarantined athletes returning to play after COVID-19 JF BMJ Open Sport & Exercise Medicine JO BMJ OPEN SP EX MED FD BMJ Publishing Group Ltd SP e000882 DO 10.1136/bmjsem-2020-000882 VO 6 IS 1 A1 Yoshitomo Saita YR 2020 UL http://bmjopensem.bmj.com/content/6/1/e000882.abstract AB