RT Journal Article SR Electronic T1 To nap or not to nap: more questions than answers JF Heart JO Heart FD BMJ Publishing Group Ltd and British Cardiovascular Society SP heartjnl-2019-315442 DO 10.1136/heartjnl-2019-315442 A1 Yue Leng A1 Kristine Yaffe YR 2019 UL http://heart.bmj.com/content/early/2019/08/16/heartjnl-2019-315442.abstract AB