Xanthine [2-14C]

Xanthine [8-14C]

Xanthine [8-3H]

Xanthosine [8-3H]

Xanthurenic acid [ring-5,7-3H]

Xanthurenic acid [ring-5,7-3H] methyl ester

Xylene, m-[ring-14C(U)]

Xylene, o-[methyl-14C]

Xylene, o-[methyl-3H]

Xylene, o-[ring-14C(U)]