patents will also do. If you work for proprietary so the patents are not yours to own, you can have the owner reference letters to stress your important roles in the product,process, formula,... and letters from famous customers such as GE, AT&T, that adopt your system. algorithm, whatever.
If you don't have those, you shouldn't try NIW in the first place.
If you don't have those, you shouldn't try NIW in the first place.