Letter from Thomas Gold to Dr Andy Sinclair, Royal Greenwich Observatory, Herstmonceux Castle, Hailsham, East Sussex, BN27 1RP, England States that they would be glad if Sinclair could visit and spend a day or so with them to discuss the problem of commensurable motions in the solar system and in particular the relation to the rings of Uranus. They know of Sinclair's leading work in this area, and would think it of great value to have a change of discussing this problem with him. The discovery of Uranus's rings is an event for solar system dynamics that is of quite rare and unusual importance, and so would be a correct explanation of the phenomenon. They believe that Sinclair's visit would be very useful for progress in this field. They hope very much that Sinclair can do this. Asks him to let them know as soon as possible, so that calendar conflicts can be avoided. 1 August 1977