Citation Hunt

The Wikipedia snippet below is not backed by a reliable source. Can you find one?

Click I got this! to go to Wikipedia and fix the snippet, or Next! to see another one. Good luck!

In page Tacticity:

"

Polymers that are formed by free-radical mechanisms, such as polyvinyl chloride are usually atactic.[citation needed] Due to their random nature atactic polymers are usually amorphous.[citation needed] In hemi-isotactic macromolecules every other repeat unit has a random substituent.[citation needed]