①Thank you for your letter of …

　　②It is a pleasure for me invite you on behalf of … to accept …

　　③Thanks so much for your letter , which arrived …

　　④I am writing to you with reference to …

　　⑤I am writing to you in connection with …

　　⑥I would be grateful if you could / would …

　　⑦I would like to know some information on …

　　⑧It will be appreciated if you can / could …

　　⑨I would also like to know if you can / could …

　　⑩I look forward to hearing from you .