Simplify the following text for a Grade 7 native English-speaking person.
Original: Of the speeches , the most famous is the funeral oration of Pericles , which is found in Book Two . Thucydides undoubtedly heard some of these speeches himself while for others he relied on eyewitness accounts .
Simplified: Thucydides heard some of these speeches himself but some of the speeches he wrote without knowing exactly what was really spoken .