The first requisite of style is choice of words, and this comes under
the head of Diction, the property of style which has reference to the
words and phrases used in speaking and writing. The secret of literary
skill from any standpoint consist... Read more of DICTION at Speaking Writing.com
Never use and with the relative in this manner: "That is the dog I
meant and which I know is of pure breed." This is an error quite
common. The use of and is permissible when there is a parallel relative
in the preceding sentence or clause. Thus: "There is the dog which I
meant and which I know is of pure breed" is quite correct.