Final regulations under sections 2036 and 2039 of the Code provide guidance on the portion of property transferred to a trust or otherwise that is properly includible in the grantor’s gross estate if the grantor has retained the use of the property or the right to an annuity, unitrust, or other payment from the property for life, for any period not ascertainable without reference to the grantor’s death, or for a period that does not in fact end before the grantor’s death. Rev. Ruls. 76-273 and 82-105 obsoleted.