How to remove "Thank you for creating with WordPress. Version 3.9.2" text in backend?

I would like to replace most of the text that relate to "WordPress". For example, Replace the text "Thank you for creating with WordPress." and "Version 3.9.2" to be empty.

However, the text of "Thank you for creating with WordPress." of "WordPress" is a link. Replacement failed. How can I do?

Thanks.