Might be a reference to this publication, they recommend North-South over the rest. https://www.researchgate.net/publication/280093617_The_Relationship_between_

Might be a reference to this publication, they recommend North-South over the rest. https://www.researchgate.net/publication/280093617_The_Relationship_between_Quality_of_Sleep_and_Geographical_Directions_during_Sleeping_Process https://www.researchgate.net/publication/280093617_The_Relat...