Magneto Removal of "/" for Duplicate Link

For SEO reasons store owners will often want to standardise the URL generation in their Magento store.so sometime duplicate link generate for the same page
Ex: :yourdomain.com/contactus/
       yourdomain.com/contacts

Both will open the same page but why two link it is not standard for SEO purpose
So,for removing "/" from url we need to update changes in the following files