The three types of Wikipedia 
Burning plastic may produce toxic fumes.
“I have no doubts as to the veracity of this statement, however it would be nice if there was a cititation so people could click on it and learn more about the topic.”
The population of Australia is 23 million.
“This seems plausible, but I really have no idea how true this sentence is, so if someone could provide a source for it that would be great.”
The Earth is flat.
“The only reason why I didn’t delete this outrageous and patently false assertion outright is because I was too afraid of the edit war that would follow.”