Critical points of the elements (data page)
CRC.a-d
David R. Lide, CRC Handbook of Chemistry and Physics, 85th Edition, online version. CRC Press. Boca Raton, Florida, 2003; Section 6, Fluid Properties; Critical Constants. Also agrees with Celsius values from Section 4: Properties of the Elements and Inorganic Compounds, Melting, Boiling, Triple, and Critical Point Temperatures of the Elements
LNG
J.A. Dean, Lange's Handbook of Chemistry, McGraw-Hill, 1999; Section 6; Table 6.5 Critical Properties
KAL
National Physical Laboratory, ; D. Ambrose, M.B. Ewing, M.L. McGlashan,
SMI
W.E. Forsythe, Smithsonian Physical Tables 9th ed., online version. Table 259, Critical Temperatures, Pressures, and Densities of Gases