Assertion: wave | /r/CapableOf | start appearing at north american sporting events
Facets:
value: during the late 1970s
type: TEMPORAL
value: during early 1980s
type: TEMPORAL
Source sentences:
text: While there is general disagreement about the precise origin of the wave, most stories of the phenomenon's origin suggest that the wave first started appearing at North American sporting events during the late 1970s and early 1980s.