State responsibility — Kinds of — For taking of, or interference with, property — Forced sales of property to Government at prices fixed by Government — Prices substantially lower than value of property — Whether a "taking" within United States International Claims Settlement Act, 1949, Section 303.

State responsibility — Claims — In general — Valuation of property — Rights and concessions to exploit reserves of crude oil and gas — Engineering method of valuation — Rights and concessions relating to undeveloped acreage — Requirement that rights must have proved of predictable value — Burden of proof — Valuation of non-negotiable bonds with principal and interest in default.