Gowers' Weblog: "Basic Logical Relationships between Statements, Converses, and Contrapositives"

Read this article, paying special attention to the parts of converses and contrapositives.

Click http://web.archive.org/web/20160620152959/https://gowers.wordpress.com/2011/10/05/basic-logic-relationships-between-statements-converses-and-contrapositives/ link to open resource.