Wolfe also championed what he called "saturation reporting," a reportorial approach in which the journalist "shadows" and observes the subject over an extended period of time. "To pull it off," says Wolfe, "you casually have to stay with the people you are writing about for long stretches ... long enough so that you are actually there when revealing scenes take place in their lives." Saturation reporting differs from "in-depth" and "investigative" reporting, which involve the direct interviewing of numerous sources and/or the extensive analyzing of external documents relating to the story. Saturation reporting, according to communication professor Richard Kallan, "entails a more complex set of relationships wherein the journalist becomes an involved, more fully reactive witness, no longer distanced and detached from the people and events reported."