Does WordNet only contains Lemmas?

Question

It seems to be an implicit assumption that wordnet only contains lemmas. Eg in Combine dictionary lemmatization with stemmer.

I feel confidant it is a correct one, the Wordnet interface refers to lemmas.

However neither in the wordnet paper1, nor in the 5 Papers on WordNet 2,3,4,5,6,7 mention the word "lemma" at all.

I am starting to have my doubts. I am looking for a high quality cite-able source to reassure my doubts. Or to correct my misunderstanding.

Referenes:

• 1 [Miller, G. A. WordNet: a lexical database for English Communications of the ACM, ACM, 1995, 38, 39-41]1

• 2 [All 5 Papers]2

• 3 [Miller, George A., et al. "Introduction to wordnet: An on-line lexical database*." International journal of lexicography 3.4 (1990): 235-244.]3
• 4 [Miller, George A. "Nouns in WordNet: a lexical inheritance system." International journal of Lexicography 3.4 (1990): 245-264.]4
• 5 [Gross, Derek, and Katherine J. Miller. "Adjectives in wordnet." International Journal of Lexicography 3.4 (1990): 265-277.]5
• 6 [Fellbaum, Christiane. "English verbs as a semantic net." International Journal of Lexicography 3.4 (1990): 278-301.]6
• 7 [Tengi, Randee I. "Design and implementation of the WordNet lexical database and searching software." Fellbaum, Christiane (réd.), WordNet: an electronic lexical database, The MIT Press, Cambridge, Massachusetts (1998): 105.]7

Answer 1

Here is the reference:

In WordNet only the base forms of words are generally represented.
...
[With regards to phrases] In general, only the base forms of words, even those making up compounds such as attorney general, are stored in WordNet

from:

The chapter:
Design and implementation of the WordNet lexical database and searching software, by Tengi, R. I.

From page 105 of the book:
Massachusetts Design and implementation of the WordNet lexical database and searching software, Fellbaum, Christiane (réd.), WordNet: an electronic lexical database, The MIT Press, Cambridge, Massachusetts, 1998

Here, base form is used as a synonym for reference form (as is printed in the section heading in a dictionary), and as wordnet defined lemma: "the heading that indicates the subject of an annotation or a literary composition or a dictionary entry".