La science et l'hypothèse
《La science et l'hypothèse》 · 第 117 页 · Section 4.4，纽结 framing 的定义性上下文
If \(K\) is a knot (i.e., embedding of \(S^1\)) in an oriented 3-manifold \(M\), we can specify a framing on \(K\) by choosing a single nowhere-zero transverse vector field \(v\) to \(K\) (Figure 4.17). Then the normal orientation on \(K\) induced by the orientations of \(S^1\) and \(M\) determines a unique way (up to isotopy) to extend \(v\) to a correctly oriented basis for each normal fiber.