Can a player bring a notebook to a high OPL tournament, or must they use a single sheet of paper?

Ruling: You can bring a notebook to a high OPL tournament as long as the only visible pages are blank.

Nuances:

• You cannot refer to notes from outside the current game being played (such as sideboard guides or decklists) until you go to sideboard
• If non-blank pages are visible, you will most likely receive a warning for general error