Sentence:  The participants <WSD>were</WSD> Professor H. Bondi , professor of mathematics at King 's College , London ; Dr. W. B. Bonnor , reader in mathematics at Queen Elizabeth College , London ; Dr. R. A. Lyttleton , a lecturer at St. John 's College , Cambridge , and a reader in theoretical astronomy at the University of Cambridge ; and Dr. G. J. Whitrow , reader in applied mathematics at the Imperial College of Science and Technology , London . 
Meaning of the word marked with <WSD> tags:  be identical to; be someone or something