The lectures notes are here.
Example 1. O conveys Blackacre “to A for life.” 0 has a reversion in fee simple that is certain to become possessory. At A’s death, either 0 or O’s successors in interest will be entitled to possession
Example 2. 0 conveys Whiteacre “to A for life, then to B and her heirs if B survives A. O has a reversion in fee simple that is not certain to become possessory. If B dies before A, O will be entitled to possession at A’s death. On the other hand, if A dies before B, O’s reversion is divested on A’s death and will never become possessory.
O conveys Blackacre “to Hartford School Board so long as used for school purposes.”