Taken from: http://camacho-english-class.blogspot.com.es/2014/07/useful-linkers-when-writing.html
Linkers and expressions for formal and informal letters
Taken from: https://helendipity.wordpress.com/2013/10/15/ni-2-letteremail-writing-formal-and-informal-expressions-2/
Essay
Taken from: https://liveinenglish.wordpress.com/2013/02/09/opinion-essay/
Taken from: http://rakeladri.blogspot.com.es/2014/05/here-you-have-some-little-help-for-next.html
English in Paradise 