One week after basketball great Julius Erving — Dr. J — went public with the news that his youngest son, Cory, was missing, investigators say they have no credible leads. Authorities confirm that they have received more than 600 tips and that police have combed lakes in the area of Florida where Cory, 19, was last seen, leaving a family picnic on Memorial Day weekend to run a 20-minute errand. Police say there has been no sign of Cory’s car, a Volkswagen Passant, either. Dr. J confirmed that Cory had a troubled past, and police have mentioned Cory’s problems with drugs and alcohol. Among those who have contacted the Erving family to offer support, says the Associated Press, are the Rev. Jesse Jackson, Bill Cosby and several NBA stars, including Michael Jordan.