The version on that Web site (& in _Rise Up Singing_) is missing a stanza that is sung at the beginning by Jean Ritchie:

Hail the blest morn when the great Mediator
Down from the regions of glory descends;
Shepherds, go worship the Babe in the manger,
Lo! for a guard the bright angels attend.

Was that added by another hand?

The Ritchies use the first stanza given as a chorus.

Incidentally, she writes "suns" for "sons" -- probably a mistake, but possibly an improvement. %^)