MADISON, Wis. (AP) – Authorities say a cold case investigation into a Waupaca County double homicide 21 years ago has led to charges in a 1990 sexual assault.  Glendon Gouker is charged with sexually assaulting a woman at a park in Iola in November 1990. The state Department of Justice says DNA evidence from the assault was resubmitted to the State Crime Lab and Gouker was found to be a contributor to the DNA.  State and local authorities say the 41-year-old Gouker is incarcerated in Oklahoma and is a person of interest in the Wisconsin double homicide. The DOJ and Waupaca County Sheriff’s Department continue to investigate the 1992 fatal stabbings of 23-year-old Tanna Togstad and 35-year-old Tim Mumbrue.  A message left for Gouker’s attorney in Norman, Okla., was not immediately returned.