Passage Summary: When history books give different dates for the same event, historians try to weed out the less reliable books and then look for outside clues to figure out which date is actually correct.

Reasoning: Historians face difficulties when sources disagree on dates; they should reduce the number of sources and then attempt to find the correct date using external evidence.

Analysis: Since this is a 'Most Strongly Supported' question, we need to find a statement that follows logically from the provided facts without overreaching. The stimulus notes that even after narrowing down sources, several often remain, and independent verification is only 'occasionally' successful. This suggests that the process of elimination doesn't always result in a single, definitive answer. Look for an answer choice that reflects this inherent uncertainty or the limitations of the historians' methods.