Physical Conditions in the Orion Nebula and an Assessment of its Helium Abundance
Baldwin, Ferland, Martin, Corbin, Cota, Peterson, Slettebak
Astrophysical Journal, 374:580--609, 1991 June 20
1991ApJ...374..580B
One of the seminal observational papers on Orion. Low/medium resolution spectrophotometry with an EW-oriented slit, extending to the W for 5 arcmin, starting from 30 arcsec W of θ1C.
Also contains extensive analysis of physical conditions in terms of a Cloudy model. However, this part is not so useful since the model is for a static, constant-pressure slab.