What are the six categories which require writing? 1) Contract for unilateral obligation for creation, transfer, variation, or extinction of a real right in land 2) Creation, transfer, variation, or extinction of a real right in land 3) Wills, testamentary trust dispositions and settlements, and codicils 4) Gratuitous unilateral obligations, except in the course of a business 5) Truster-as-trustee trusts 6) Agreement under s.66(1) of the Land Registration etc (Scotland) Act 2012