A joint interest is one owned by several persons in equal shares, by a title created by a single will or transfer, when expressly declared in the will or transfer to be a joint tenancy, or by a transfer from a sole owner to himself and others, or from tenants in common to themselves, or to themselves and others, when expressly declared in the transfer to be a joint tenancy, or when granted or devised to executors or trustees as joint tenants. No joint tenancy shall be created except as herein provided. SOURCE: CC § 683.