Dear Sir,
  I wish to apply for a position with your company as a regional sales manager. I am twenty-nine years old and at present employed by the Xishan Company,where I have been working as an assistant manager for the past four years. Before that, I had spent three years as a sales agent in the Taiji Company.
  My only reason for leaving my present position is to better myself as I feel I have potential(潜力) for greater things. I wish to serve in a large company like yours so that I can learn new things and give full play to my talent.
  I can give you references from both of the firms mentioned above as to my character and ability. Enclosed please find my resume.
  I would appreciate your considering my application. I am looking forward to hearing from you soon.
  Sincerely yours,