The most controversial aspects of Proposition 71 will have strict oversight, experts speaking at a Stanford University forum said Tuesday. A procedure called nuclear transfer, or therapeutic cloning, is central to research on stem cells. Because it involves the creation and destruction of embryos to study diseases and cures, ``it may offend some people,'' said Paul Berg, professor emeritus of molecular and genetic medicine at Stanford and a 1980 Nobel Prize winner. ---snip--- Berg said therapeutic cloning -- in which stem cells are harvested from a cloned embryo -- provides greater scientific opportunities than other methods of obtaining stem cells....