fabio.mazzarino

In-Post Template plugin add additional content to posts and pages, inside the_content() data result. It can be used to add sitewide content like AdSense, banners and plugins.
It accepts to insert html, java script, embedded content, php and even others plugins. Template tags are also accepted.
It replaces a special mark added inside the post which can be the  mark or any other configured.

In-post Template

In-Post Template plugin add additional content to posts and pages, inside the_content() data result.

E. Marten

You need to use WordPress SEO by Yoast (Props to him!)
Adds “More Sitemaps” to your WordPress SEO Settings. If you are using a second WordPress-Installation in a subdirectory, you can now easily add the second Sitemap into the main one.
If you are using a second WordPress-installation in a subdirectory and want it to be fully integrated it into your main site to prevend struggeling with two or more Sitemaps in your Webmastertools, 
you can easily integrate more sitemaps into your main one. (sitemap_index.xml) 
The Plugin adds your second and third (aso) sitemap into the main sitemap and tooks care about the modification date automatically!
Thanks to Joost de Valk!

IsSiY (Include second Sitemap into Yoast) WordPress SEO Extension

Adds "More Sitemaps" to your Wordpress SEO Settings. Include differen sitemaps to your sitemap_index.xml

In-post Template vs IsSiY (Include second Sitemap into Yoast) WordPress SEO Extension