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C. Austen Angell has been a great inspiration for liquid and glass scientists including myself. He was a close collaborator of mine on glass dynamics and thermodynamics, particularly on the sub-Tg relaxation in glass. Here, in memory of his seminal contributions to science and our collaboration, I revisit our published data and analyze our unpublished data, as well as review some of important results reported recently in the literature, concerning the sub-Tg relaxation in glass, a field on which Austen has profoundly impacted. I highlight new insights into the dynamics, thermodynamics, and structural heterogeneity in glass far from equilibrium, based on the hyperquenching-annealing-calorimetry (HAC) experiments. I describe key extensions and applications of the HAC approach in glass research. Finally, I present the perspectives and challenges regarding the sub-Tg relaxation in glasses with fictive temperatures well above Tg.