answer: #Person1# invites #Person2# to #Person1#'s birthday party. #Person2# thanks for the invitation but is not sure.
documents: #Person1#: The nineteenth of June is my birthday. I'm planning to have a small party. Would you like to come?
  #Person2#: Happy birthday to you! I'd really love to come, but I'm not sure right now. I'll try to make it. Thank you for your invitation.