ebrary, Inc, Wratil, M., & Gallmann, P. (2011). Null pronouns. De Gruyter Mouton.
芝加哥风格引文ebrary, Inc, Melani Wratil, 与 Peter Gallmann. Null Pronouns. Berlin ; Boston: De Gruyter Mouton, 2011.
MLA引文ebrary, Inc, et al. Null Pronouns. De Gruyter Mouton, 2011.
警告：这些引文格式不一定是100％准确.