|journal=Optics and Spectroscopy|volume=89 |issue=1 |pages=145–147 |year=2000 |last1= Okulov |first1=A Yu|doi=10.1134/BF03356001 |bibcode=2000OptSp..89..131O|url=https://www.semanticscholar.org/paper/0bd2d3e9a6912a188f42b50316f4652c165d1b6b}}</ref>.<ref name="Okulov, A Yu 2020">{{cite journal |title=Structured light entities, chaos and nonlocal maps | |journal=Optics and Spectroscopy|volume=89 |issue=1 |pages=145–147 |year=2000 |last1= Okulov |first1=A Yu|doi=10.1134/BF03356001 |bibcode=2000OptSp..89..131O|url=https://www.semanticscholar.org/paper/0bd2d3e9a6912a188f42b50316f4652c165d1b6b}}</ref>.<ref name="Okulov, A Yu 2020">{{cite journal |title=Structured light entities, chaos and nonlocal maps |