the main idea is presented in this sentence:
There were many facts that hinted that dragons may not be fictional.
The three details from the texts that supports the main idea are:
1) People of different cultures describe dragons in similar ways. Each culture serve as witnesses to other cultures testimonies regarding dragons.
2) Dragons are mentioned not only in stories but also in old legal papers, in the travel logs of Marco Polo, and in the Bible.
3) Dragons are included along with eleven real animals in the Chinese calendar.