(70 ILCS 2805/13)
(from Ch. 42, par. 424)
At the time of or before incurring any indebtedness, the board of
trustees shall provide for the collection of a direct annual tax sufficient
to pay the interest on such debt as it falls due, and also to pay and
discharge the principal thereof, as the same shall fall due, and at least
within twenty years from the time of contracting the same.
(Source: Laws 1935-36, Fourth Sp. Sess., p. 16.)