Which drawings need protection?
1A local gallery has a single visitor guide for a new exhibition. The guide, which contains a map of the rooms, is available at the entrance. The map helps visitors find a drawing workshop, but the guide also explains the exhibition's theme. It is not a special version reserved for workshop participants.
2Some drawings in the exhibition were made with fragile natural colours. Other drawings used more stable materials. The drawings that use natural colours are kept away from direct sunlight. This rule identifies a particular group; it does not say that every drawing uses the same materials.
3An editor preparing a notice removed the commas around which contains a map of the rooms and added commas around that use natural colours. The curator asked for a revision. The notice needed to preserve both the single guide's extra feature and the distinction between the two groups of drawings. A small punctuation change should not silently change which objects a description includes.