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Dear [YOUR FRIEND'S NAME],
I would like to invite you as my guest in March of 2009. I can arrange your travel and accommodation. During your stay here in (NAME OF CITY), you can visit the following places, and many other interesting locations in the city, too:
If you have any other locations in mind, please let me know.
Please be assured that I shall provide all the help needed to make your visit comfortable. However, it would be worthwhile to prepare a detailed program to avoid confusion later.
Best regards,
YOUR NAME