Warren, W. H. Jr.; Hesser, J. E. (June 1977). "A photometric study of the Orion OB 1 association. I - Observational data". Astrophysical Journal Supplement Series. 34: 115–206. Bibcode:1977ApJS...34..115W. doi:10.1086/190446.
Warren, W. H. Jr.; Hesser, J. E. (April 1978). "A photometric study of the Orion OB 1 association. III - Subgroup analyses". Astrophysical Journal Supplement Series. 36: 497–572. Bibcode:1978ApJS...36..497W. doi:10.1086/190510.
Warren, W. H. Jr.; Hesser, J. E. (June 1977). "A photometric study of the Orion OB 1 association. I - Observational data". Astrophysical Journal Supplement Series. 34: 115–206. Bibcode:1977ApJS...34..115W. doi:10.1086/190446.
Warren, W. H. Jr.; Hesser, J. E. (April 1978). "A photometric study of the Orion OB 1 association. III - Subgroup analyses". Astrophysical Journal Supplement Series. 36: 497–572. Bibcode:1978ApJS...36..497W. doi:10.1086/190510.