invitation letter sample

the requirements for S1 visa of my daughter need an invitation letter from my side. it must be a simple letter from my side, or I need to authorize it from some agency in china? if some one can please post of sample of this kind of invitation letter

You can apply for an S1 type for your baby. You need to provide those documents: baby’s passport and its photocopy, the application form affixed with a passport-style photo, """"an invitation letter"""""" from you and copies of your passport and residence permit in China, as well as the baby’s birth certificate, and other materials the consular officer consider necessary.