In the News & Views article “Atomic physics: A whiff of antimatter soup” by Clifford M. Surko (Nature 449, 153–155; 2007), the first prediction of the positronium atom is ascribed to John Wheeler in 1946. In fact the story, as recounted for example by Helge Kragh (H. Kragh J. Chem. Educ. 67, 196–197; 1990), is more complex: Stjepan Mohorovic̆ić proposed a similar 'electrum' atom in 1934, although the antiparticles of his system were not the positrons of quantum theory; and Arthur E. Ruark, in work published in 1945 and at the time unknown to Wheeler, coined the term 'positronium' for “an unstable atom composed of a positron and a negative electron”.

In the same News & Views article, it is also stated that a γ-ray laser could be made from a Bose–Einstein condensate of positronium molecules (Ps2); in fact, positronium atoms (Ps) would be the starting point.