I recently had to get a new passport in order to process a Hong Kong working visa, as my previous passport was only valid for another 11 months. However, my old passport contains my China residence permit, (still valid for another 10 months). Do I need to get a new visa, or get my residence permit transferred from my old passport to the new one, or can I just bring both passports to the airport, in order to re-enter China? If I can just bring both passports, which passport number should I use to book the flight? Thanks in advance.