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Absolute triply differential (e,2e) cross section measurements are presented for H (for incident energies, E0, of 15.6 and 17.6 eV) for equal energy sharing and the θ12 = π configuration. Results of distorted partial wave calculations agree with the measurements; those of convergent close coupling calculations agree with the relative angular distributions, but are lower than experiment by factors of from 2 to 7. Relative experimental results for H for E0 = 14.6 eV show a qualitative change in shape, which agrees with theory. Implications of the absolute experimental results for the range of validity of the Wannier threshold law are discussed.