Distance between domains in the sense of Letho is not a metric. Božin, Vladimir; Marković, Vladimir — 1999 Annales Academiae Scientiarum Fennicae. Mathematica
A proof of an Aljančić hypothesis on 𝒪 -regularly varying sequences. Đurčić, Dragan; Božin, Vladimir — 1997 Publications de l'Institut Mathématique. Nouvelle Série