Implications of turning off the "Influence" of "Bone Copy Rotation Constraints" for certain "Local Axes" - CG Cookie | Learn Blender, Online Tutorials and Feedback
animation - Copy Rotation Problem - Blender Stack Exchange
Copy Rotation | Bone Constraints | Blender Tutorial - YouTube
How to Animate Gears in Blender [TUTORIAL] - Yarsa DevBlog
Daily Blender Tip - Copy Rotation from one object to another - BlenderNation
Solved: Is it possible to copy rotation from two objects to a single object at the same time? - Autodesk Community - Maya