Assertion: precession | /r/CapableOf | remain difficult to account
Facets:
value: as a group
type: MANNER
Source sentences:
text: The lunar apsidal precession was not accounted for in Claudius Ptolemy's Almagest, and as a group these precessions, the result of a plethora of phenomena, remained difficult to account for until the 20th century when the last unidentified part of Mercury's precession was precisely explained in Albert Einstein's general theory of relativity.[citation needed]