Algebraic Topology
《Algebraic Topology》 · 第 489 页 · Section 4.L
The Steenrod squares are operations \(\operatorname{Sq}^i:H^n(X;\mathbb Z_2)\to H^{n+i}(X;\mathbb Z_2)\) satisfying naturality, additivity, the Cartan formula, suspension stability, and the dimension conditions.