Multicolour deep CCD photometric study of the moderately young southern open star clusters NGC 3228, NGC 4103, NGC 5662 and NGC 6087R. Sagar and R. D. CannonAstron. Astrophys. Suppl. Ser., 122 1 (1997) 9-29DOI: https://doi.org/10.1051/aas:1997293