Dear__________,
I am writing this letter to call on_________.As some of you may know,________.In face,________.
It is necessary for us to________.On the one hand,__________.On the other hand,_________.Hesce, it is high time________.Firstly, we should _____________.Secondly,___________.
Please contact us via_________.Please join us in the effort to __________.
Thank you for your paiticipation
Sincerely,
____________