As well as old leases, you should keep anything that documents the landlord-tenant relationship or supports the items you report on your tax return. If the IRS audits your tax return and you cannot produce the correct verification documents, you may be liable for additional tax and penalties.
The facet joints link the vertebrae together and give them the flexibility to move against each other. The facets are the bony knobs that meet between each vertebra. There are two facet joints between each pair of vertebrae, one on each side.
A craniovertebral joint is exactly what it sounds like: a joint that permits movement between the vertebral column and the skull. The ligaments in the spine support and reinforce the joints between the vertebrae. The atlas and axis in particular work with the ligaments to move the neck. The atlas and the occipital bone form the atlanto-occipital joint, which allows neck flexion. When you nod your head as if to say yes, that is neck flexion. The atlas and axis form the atlanto-axial joint, which allows head rotation.