为父母（国内）申请绿卡，最近收到visa center的 email，要我 pay fees, submit visa application form, collect financial documents and collect supporting documents. The website shows a list of supporting documents.
请教各位大师，which documents are applicable to my parents cases? 我申请I-130的时provided my birth certificate and their marriage certificate. Do i need to provide others (i.e., their birth certificates, photocopy of valid passport biographic data page, police certificates)? If we do need to provide Police Certificate, what is it?
