Child theme created, but parent stylesheet still referenced in rendered code

I have created a child theme and think I've done it correctly, but the parent stylesheet is still referenced when I view source on the actual website. What can I do to make the Child stylesheet take precedence? I can't seem to find the actual PHP that calls for the stylesheet in the header, and it appears to be hard-coded to look for the parent theme rather than being dynamic to pull in the stylesheet of the active theme.

Hi there!
Stylesheets included to the pages in file library.php in function headtext().