Assertion: polycythemia's cause | /r/HasProperty | obstructive sleep apnea
Facets:
Source sentences:
text: The most common causes of secondary polycythemia include obstructive sleep apnea, obesity hypoventilation syndrome, and chronic obstructive pulmonary disease (COPD).  
text: The most common causes of secondary polycythemia include obstructive sleep apnea, obesity hypoventilation syndrome, and chronic obstructive pulmonary disease (COPD).