Rasarnavasudhakara 3.14

3.14

atha patākā--
yat pradhānopakaraṇa-prasaṅgāt svārtham ṛcchati |
sā syāt patākā sugrīva-makarandādi-vṛttavat ||

Now, the episode: / That which attains its own purpose through the incidental service of the principal purpose / is an episode, like the story of Sugrīva, Makaranda, and others.