End T4_2.
Hint Resolve not_col_permutation_1 not_col_permutation_2
not_col_permutation_3 not_col_permutation_4 not_col_permutation_5 : col.
Section T4_3.
Context `{Tn:Tarski_neutral_dimensionless}.

Lemma col_trivial_2 : forall A B, Col A B B.