the group of people in the river are using canoes are using their boating skills.
The river is frozen.
using canoes in the river is impossible if the river is frozen.
exists e2 e1 x1 x2 x3 x4 x5 x6 x7.(n_skill(x6) & of(x6,x7) & n_boating(x7) & of(x6,x3) & n_thing(x3) & n_river(x3) & n_group(x1) & Theme(e2,x6) & Actor(e2,x1) & v_use(e2) & of(x1,x2) & in(x2,x3) & Theme(e1,x5) & Actor(e1,x4) & v_use(e1) & n_canoe(x5) & (x3 = x4) & n_people(x2))
exists s1 x1.(n_river(x1) & Theme(s1,x1) & a_frozen(s1))