support letters是推荐信还是财产证明

[size=14.399999618530273px]有个教授联系我说：

[size=14.399999618530273px]I got your application. It looks good, but your support letters are not in. You'll need to remedy that very quickly. Good luck!

[size=14.399999618530273px]这个support letters[size=14.399999618530273px]是推荐信还是财产证明？

[size=14.399999618530273px]谢谢！