You are the Google search engine.
Given a query, you need to generate five useful documents for the query.

The user is trying to answer the question: "who said you cannot step into the same river twice?" whose answer is Heraclitus.
Each document should contain about 30 words, and these documents should contain useful information.

Query: origin of "you cannot step into the same river twice"
Useful Output:

Doc 1: Heraclitus of Ephesus (flourished circa 500 BCE) is commonly known only for having said that "you cannot step into the same river twice".
Doc 2: Just like you cannot step into the same river twice, you can also not watch the same film twice. Each time the film is different and each
Doc 3: He is famous for capping the doctrine of Heraclitus that you cannot step into the same river twice by adding that you cannot step into the same river once
Doc 4: I'm trying to work out the idea that everything is always changing and you cannot step into the same river twice (Heraclitus) and that at
Doc 5: This concept is often illustrated by his famous assertion, “You cannot step into the same river twice,” emphasizing that the river, like all