^ 1.01.1New Techniques in the Manufacture of Platinum-Iridium Mass Standards, T. J. Quinn, Platinum Metals Rev., 1986, 30, (2), pp. 74–79
^Water Structure and Science, Water Properties, Density maximum (and molar volume) at temperature of maximum density, a (by London South Bank University). Link to Web site. （页面存档备份，存于互联网档案馆）
^The Third Periodic Verification of National Prototypes of the Kilogram (1988–1992), G. Girard, Metrologia 31 (1994) 317–336
^The other two Pt‑10Ir standards owned by the U.S. are K85, which is used for watt balance experiments (see Watt balance, above), and K650, which was an early attempt with a new series of prototypes (K64–K80) that were diamond-turned directly to a finish mass. K650 has a density of 7004215353700000000♠21.53537 g/ml, which is normal for Pt‑10Ir alloy. However, as its finished mass was roughly 2000 µg less than one kilogram, it is unsuitable for use as a national prototype and is instead known as a mass “standard”—not a “prototype”. However, it serves well for special duties, such as a stability reference when K4 and K20 are transported to the BIPM and back. There are three other diamond-turned, Pt‑10Ir replicas that are not formally considered to be “prototypes”: K651, K690, and K691.
^The Kilogram and Measurements of Mass and Force, Z. J. Jabbour et al., J. Res. Natl. Inst. Stand. Technol. 106, 2001, 25–46 (3.5 MB PDF, here （页面存档备份，存于互联网档案馆）)
^Before the BIPM’s published report in 1994 detailing the relative change in mass of the prototypes, different standard bodies used different techniques to clean their prototypes. The NIST’s practice before then was to soak and rinse its two prototypes first in benzene, then in ethanol, and to then clean them with a jet of bi-distilled water steam.
