States as international persons — In general — Sovereignty and independence — Waiver of rights — Estoppel — As a principle of substantlve law — Nature of principle — Whether Party estopped by official maps issued under influence of error in Award Map Whether Party on whose maps Award Map based responsible for error — Whether under legal duty to inform other Party or Arbitrator of error — Whether Party precluded by statements in diplomatic correspondence — Relevance of object of correspondence, state of geographical knowledge — Necessity that Parties be ad idem as to terms used.

Disputes — Arbitration — Evidence — The "critical date" — Meaning of — Whether the same for all purposes.

Disputes — Arbitration — The Award — Scope and Binding Force of — Error — Geographical error — Effect of — Extent to which boundary settled by A ward and Demarcation — Whether error effects a total rupture — Competence of Mixed Boundary Commission to settle boundary — Whether decision invalidated by error in own maps Interpretation of Award — Intention of Arbitrator — Relevance of preparatory work and subsequent acts of parties — " Interpretation and fulfilment " — Meaning of phrase — Whether referring to fulfilment by Parties or by Court — Interpretation of direction that boundary follow river — Whether it must follow major channel Historical and scientific evidence of major channel — Scientific criteria — Whether necessary to follow river to source when description affected by error.

State Territory — Parts of — Boundaries — Land boundaries — Determination by Arbitral Award — Effect of geographical error Fulfilment of Award by Parties — Estoppel — Part of boundary line following named river — Identification of river — Effect of division of river into two channels — Criteria for selection of appropriate channel.