These books are great resources for learning about machine kinematics and metal cutting tools. When using them, handle with clean hands to avoid adding more soiling. Keep them in a dry place to prevent further foxing and damage. You can use bookmarks to mark important pages. If you want to keep them in the best possible condition, store them on a bookshelf away from direct sunlight. When you're done reading, close them gently to preserve the stiff bindings.