Numbering system for sigma Orionis

   1 -  49 : Béjar V.J.S., et al. 1999, ApJ 521, 671
  50 -  69 : Zapaterio Osorio M.R., et al. 2000  Science 290, 103
  70 -     : Zapaterio Osorio M.R., et al. 2002, ApJ 578, 536
  71 -     : Barrado y Navascues D., et al. 
 101 - 172 : Numbering by order of inclusion in the database
             See the Notes for proper identifications 
 201 - 335 : Scholz A., Eisloeffel J. 2004, 419, 249 (No + 200)
 350 - 397 : Béjar V.J.S., et al. 2004, Astron. Nachr. 325, 1 (No + 300)
 401 - 634 : Sherry W.H., et al. 2004, AJ 128, 2316 (No + 400)
 701 - 763 : Weaver W.B., Babcock A. 2004, PASP 116, 1035 (No + 700)