Calculation of the mean of an observable in quantum mechanics is typically assumed to require that the state vector be in the domain of the corresponding self-adjoint operator or for a mixed state that the operator times the density matrix be in the trace class. We remind the reader that these assumptions are unnecessary. We state what is actually needed to calculate the mean of an observable as well as its variance.

Originally published by Ballinger, this book is a result of an Atlantic Council study of U.S. international relationships on energy. It examines the uncertainties of a political, strategic, economic, and technological nature that are involved in energy supply, as well as the unavoidable certainty of finite resources.

In 1981, the Atlantic Council's Energy Policy Committee, in collaboration with the Japanese Committee for Energy Policy Promotion and the Japanese Institute of Energy Economics, published a joint policy paper entitled 'U.S.-Japan Energy Relationships in the 1980s.'.