All the supporting documents I sent for the I751 (bank statements, joint tax returns, joint bills, etc.) plus all the supporting documents we've accumulated since then, such as the 2022 tax return, the most recent joint bills, bank statements, etc. I also sent them a certified copy of the marriage license, spouse proof of citizenship, copy of the green card, copies of passport pages showing dates traveled outside the US, photographs of family gatherings, vacations together, boarding passes and hotel reservations for vacations, etc.