The PVT properties of seawater were calculated from the sound speed data of Chen and Millero (1977d) over the range of 0 to 40%. salinity, 0 to 40°C, and 0 to 1000 bars….
Chen, Chen-Tung, and Frank J. Millero. 1978. "The equation of state of seawater determined from sound speeds." Journal of Marine Research 36, (4). https://elischolar.library.yale.edu/journal_of_marine_research/1450