如何通过单点登录提供商进行身份验证后注销？

I am trying to provide authentication facility through third party single sign on provider like rpxnow. After login on every refresh of page I am not able to retrieve the cookies set by the provider so that I can delete them when user desires to log out? Is there any other way to gracefully logout the user without trying to search for cookies etc., or releasing the token provided by them after authentication?I am trying to provide authentication facility