http://www.englishpage.com/verbpage/presentperfectcontinuous.html
http://eoienglishcorner.wordpress.com/tag/present-perfect-continuous/
Just a few ideas and suggestions in order to be able to distinguish pres perf cont and practise using it.
remember all of this corresponds to 3B
Don´t forget to study English and USE IT !!!
Happy weekend! Time to stop because I HAVE BEEN WORKING FOR A LONG TIME.
Regards
Paco