Symplectic Geometry
《Symplectic Geometry》 · 第 17 页 · Section 1.8，Definition 1.8.1 及其后 trivial link 的定义
A link is a finite disjoint union of knots: \(L=K_1\cup\cdots\cup K_n\). […] A link is trivial if all of its components are trivial knots and they are “unlinked”. Equivalently, a link is trivial if its components bound disjoint discs.