Chromatic Homotopy Theory
《Chromatic Homotopy Theory》 · 第 281 页 · Section 9.2.8，Definition 9.2.23、三维流形及剖分上下文，Figure 9.7 原图
Let \(M\) be a compact 3-manifold with (possibly empty) boundary. As every smooth compact manifold, \(M\) has a triangulation \(T\), made of a certain number \(t\) of tetrahedra. […] A normal surface is a properly embedded surface \(S\) transverse to \(T\) that intersects every tetrahedron into triangles or squares as in Figure 9.7.