"Wow, that was close," Gloot breathed as silence descended again. "Those boys are the City Guard. They don't mess around."
"Permanent cadre?" Retief asked.
"Right. Eight on, eight off. Of course, most of 'em got off-duty jobs with the major mobs; but when shift time arrives they fall in for duty, even if the mob happens to be in the middle of a shoot-out with the guard at the time."
"That could be a trifle confusing."
"Yeah, but they got ground rules. When the whistle blows, there's a five-minute time-out while the cops and robbers change sides."
"A civilized system," Retief conceded.
Retief's Ransom (1971)