Griffiths, PhillipPhillipGriffiths2020-10-062020-10-06https://hdl.handle.net/20.500.12111/7922*Notes of a talk given at IMSA at the University of Miami, October 5, 2020. Based on work in progress with Mark Green and Colleen Robles. An earlier version of these notes is in https://hdl.handle.net/20.500.12111/7910.en-USPeriod mappingLecture/speech