WordPress File wp-includes/link-template.php

prev_post_rel_link()

Displays the relational link for the previous post adjacent to the current post.

self_admin_url()

Retrieves the URL to the admin area for either the current site or the network depending on context.

site_url()

Retrieves the URL for the current site where WordPress application files (e.g. wp-blog-header.php or the wp-admin/ folder) are accessible.