Subquadrangles of Generalized Quadrangles of Order (q2, q), q Even

First, we survey the known generalized quadrangles of order (q2, q), q even, including a description of their known subquadrangles of order q. Then, in the case of Titsʹ generalized quadrangles, we completely classify the subquadrangles of order q, while in the case of the flock quadrangles we classify the subquadrangles of order q which contain the base point. Finally, we determine the full automorphism groups of the Tits generalized quadrangles T2(O) of order q and T3(Ω) of order (q, q2).