You can find many templates for sponsorship request letters on the Internet. Some are paid services, but many are free. You should read these letters to get a sense of the format and content.  Don't copy a sample letter too closely, though. You need to tailor your letter to the organization you're writing to so it sounds personal and not too formulaic.   For example, if you know a CEO has a personal background that relates to your cause, you can personalize the letter to that person. You should know the background of the people or companies you're soliciting, and you should tailor the letters so they feel personal. Tone will depend on audience.  However, you should always be professional and not too colloquial in a sponsorship letter.  Put the letter on formal letterhead that has the logo and name of your organization. This will make your request look more professional. If you're asking for a sponsorship for yourself, you could still create professional letterhead that has your name at the top in a nice font. If you're writing to a business or other organization, more formal is best. If you're writing to a family member or friend, you could be less formal, but you still shouldn't be so casual you sound disrespectful. Whipping off an informal email is unlikely to get good results in either case. A typical sponsorship letter uses the format seen in many business letters. You should use the right structure or it won't look professional.  Start the letter with the date, and then the sponsor's name and address. Then, after a space, put the salutation: Dear (Name of the person) and a comma. Keep it short. Keep the sponsorship letter on one page. People are unlikely to have time to read more. Most people being solicited will give about a minute to your sponsorship letter. So in addition to keeping it on one page, make sure the language is concise and clear.   Send it snail mail. Email requests make it seem like you didn't take much care when sending it. At the end of the sponsorship letter, you should thank them for...

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Write a summary of the previous text in Vietnamese:
Hãy nghiên cứu một vài mẫu thư ngỏ mời tài trợ. Chọn lối diễn đạt phù hợp. Hãy sử dụng mẫu thư kinh doanh tiêu chuẩn. Hãy kết thúc lá thư với lời cảm ơn.