Symplectic Geometry
《Symplectic Geometry》 · 第 144 页 · Section 6.6，Definition 6.6.4（普通 signature；不指参数化的 ω-signature）
The signature of a link \(L\), written \(\sigma(L)\), is the signature of \(M+M^{\mathrm T}\) where \(M\) is any Seifert matrix for \(L\). […] The signature of a diagonal matrix is the number of positive entries minus the number of negative entries. […] More importantly for us, congruence preserves signature — a result known as Sylvester’s Theorem.