Proved equivalence of Ord and Ord_alt. Proved ordertype_eq_imp_ord_iso, le_well_ord_Memrel, le_ordertype_Memrel, lt_oadd1, oadd_le_self, bij_0_sum, oadd_0, oadd_assoc, id_ord_iso_Memrel, ordertype_0. Now well_ord_Memrel follows from le_well_ord_Memrel and ordertype_Memrel follows from le_ordertype_Memrel. Proved simpler versions of Krzysztof's theorems Ord_oadd, ordertype_pred_subset, ordertype_pred_lt, ordertype_pred_unfold, bij_sum_0, bij_sum_succ, ordertype_sum_Memrel, lt_oadd_disj, oadd_inject. Deleted ordertype_subset: subsumed by ordertype_pred_unfold. Proved ordinal multiplication theorems Ord_omult, lt_omult, omult_oadd_lt, omult_unfold, omult_0, omult_0_left, omult_1, omult_1_left, oadd_omult_distrib, omult_succ, omult_assoc, omult_UN, omult_Limit, lt_omult1, omult_le_self, omult_le_mono1, omult_lt_mono2, omult_le_mono2, omult_le_mono, omult_lt_mono, omult_le_self2, omult_inject.