The Arithmetic of Elliptic Curves
《The Arithmetic of Elliptic Curves》 · 第 324 页 · Chapter X，Section 3「Homogeneous Spaces」，Definition
Two homogeneous spaces $C/K$ and $C'/K$ for $E/K$ are equivalent if there is an isomorphism $\theta:C\to C'$ defined over $K$ compatible with the action of $E$. The collection of equivalence classes of homogeneous spaces for $E/K$ is called the Weil–Châtelet group for $E/K$ and is denoted by $WC(E/K)$.