text: IAEA issues official certificates of isotopic composition for most new calibration materials. The IAEA has certified isotopic values for [https://nucleus.iaea.org/rpst/Documents/VSMOW2_SLAP2.pdf VSMOW2/SLAP2] and [https://nucleus.iaea.org/rpst/referenceproducts/ReferenceMaterials/Stable_Isotopes/13C18and7Li/IAEA-603/RM603_Reference_Sheet_2016-08-16.pdf IAEA-603] (the replacement for the NBS-19 CaCO standard). However, the isotopic composition of most reference materials distributed by IAEA are established in the scientific literature. For example, IAEA distributes the N isotope reference materials USGS34 (KNO) and USGS35 (NaNO), produced by a group of scientists at the USGS and reported in Böhlke et al. (2003), but has not certified the isotopic composition of these references. Moreover, the cited δN and δO values of these references were not reached through interlaboratory comparison. A second example is IAEA-SO-5, a BaSO reference material produced by R. Krouse and S. Halas and described in Halas & Szaran (2001). The value of this reference was reached through interlaboratory comparison but lacks IAEA certification. Other reference materials (LSVEV, IAEA-N3) were reached through interlaboratory comparison and are described by the IAEA but the status of their certification is unclear.