Just a quick thought from a recent presentation as quoted below:
Contact Spheres are businesses or professions that naturally provide a source of referrals for one another. They are in somewhat related but non-competing businesses. Business in a Contact Sphere have a symbiotic relationship in that they support and enhance one another.
“Power Circles” and “Strategic Relationships” are similar terms often referring to this same concept. Who have you found to “support and enhance” with your business recently?