The Starfleet Handbook on Personal Relationships was a guide to Starfleet officers and crew on how to deal with personal relationships, with alien species and presumably within those of the same species. It was three centimeters thick.
In 2375, upon being reminded about the extensiveness of the publication, Harry Kim quoted a portion of it to Captain Kathryn Janeway: "All Starfleet personnel must obtain authorization from their CO as well as clearance from their medical officer before initiating an intimate relationship with an alien species." She congratulated him on his recitation of the passage, but informed him that it came too late, as Kim's unsanctioned romantic relationship with Derran Tal had already begun to have a deleterious effect on his health. (VOY: "The Disease")
