Between 2006 and 2010, investigators collected millions of telephone records covering calls made in and around La Plata in the days surrounding López's disappearance. The investigation identified two persons of interest: a retired police doctor who visited Etchecolatz in prison at Etchecolatz's request before the disappearance, and a retired officer photographed near a human rights activist's home on the day López vanished. Neither was charged with the abduction. Using only open-source intelligence methodology, describe the sequence of steps you would use to build a network map connecting these individuals to each other, to Etchecolatz's prison communications, and to the Buenos Aires Provincial Police structure of the 1970s.