corpus (one-timers) is to show that the proportion of new words in the one-timers is half
that in the recurring words.
References
Nation, I. S. P. (2004). A study of the most frequent word families in the British National
Corpus. In P. Bogaards & B. Laufer (Eds.), Vocabulary in a Second Language:
Selection, Acquisition, and Testing (pp. 3-13). Amsterdam: John Benjamins.
Nation, I. S. P., & Webb, S. (2011). Researching and Analyzing Vocabulary. Boston:
Heinle Cengage Learning.