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: "what caused the collapse of the han dynasty?" whose answer is Yellow Turban Rebellion.
Each document should contain about 30 words, and these documents should contain useful information.

Query: causes of the collapse of the Han Dynasty
Useful Output:

Doc 1: Economic Hardships and External Threats · Internal Power Struggles and Corruption · Historical Context and Cultural Significance · Confronting
Doc 2: Income Inequality May Have Caused the Collapse of the Roman Empire and Han Dynasty. Learn more about how income inequality may increase the
Doc 3: The Western Han ended in 9 A.D. when government official Wang Mang took advantage of long-term internal disarray to seize the throne and try to
Doc 4: Internal Corruption · Internal Conflict Over Taxation · The Steppe Societies · The Weakening of the Xiongnu · Warlordism and Breakdown into Regions.
Doc 5: For the first video of the year, we look at reasons the Han Dynasty collapsed, as well as how the reasons are similar to the collapse of the