  In this paper, we calculate the $ \phi (\hat{\phi})-$Selmer groups $
S^{(\phi)} (E / \Q) $ and $ S^{(\hat{\varphi})} (E^{\prime} / \Q) $ of elliptic
curves $ y^{2} = x (x + \epsilon p D) (x + \epsilon q D) $ via descent theory
(see [S, Chapter X]), in particular, we obtain that the Selmer groups of
several families of such elliptic curves can be arbitrary large.
