四分律行事鈔資持記 3.226

3.226

次師，初科，三義。據體立宗，故《四分》先準。本宗既闕，取外相成，故取諸部。本異俱無，仍加義決。下之二種，對上本宗，故云旁出；旁即兼也。

The second master: the first section has three meanings. Establishing the school based on essence, the Dharmaguptaka-vinaya is followed first. When this school is deficient, taking external schools to complement it, one therefore draws upon the various schools. When both this and other schools lack it, one still adds determination by principle. The lower two kinds, in contrast to this main school above, are therefore said to be 'collaterally derived'; collateral means complementary.