Reference help

[Oklahoma official]

Baseline throw-in on offensive end, when offensive players line up perpendicular, I know defensive players do not have to be allowed between the offensive players, but where in the book (NFHS) does it reference it or in the case book? I also know that when the offense lines up within 3 feet of end line, shoulder to shoulder, the defense can ask and be allowed to be between the offensive players, if they are more than 3 feet from the end line, you don't have to allow it. But I need a reference for the perpendicular line up,