U.S. Government UFO Report (Catalogue):

“Summary of Sightings of Unknown Phenomena,
17th District OSI” (Selected Cases)

(Air Force Office of Special Investigations, 
U.S. Air Force, Washington, D.C.)
(NICAP.org)

Quote from NICAP.org’s “1949 UFO Chronology and the Grudge Report” (nicap.org):
“This chronology is currently a 29-page report and a very important year in UFOlogy.  I want to thank all the members of the A-Team who made this possible.  To look at and/or print all the 1949 Blue Book monthly summaries, click here. Otherwise the monthly listings are inserted within this chronology by month. Note: There are 209 entries in the 38-page La Paz catalog, the ‘Summary of Sightings of Unknown Phenomena, 17th District OSI’.  But in the 1949 group there were 144 sightings and the only ones listed here are the reports with some important details to make them extraordinary. Also, brief case descriptions giving the category number, name of witness, and source in brackets (M=military), are NICAP UFO Evidence entries that haven't been located. Finally, I want thank Loren Gross for thoughtfully and diligently collecting data many years ago for his UFO Histories and supplemental notes, in particular here the year 1949. And a big thanks to CUFOS and Mary Castnor for housing them on the CUFOS site.”

The Air Force Office of Special Investigations presents UFO sighting reports from 1943 through early 1950:

http://www.nicap.org/lapazcat/AFOSI_LaPazCatalograwdata.pdf

Wikipedia article: “U.S. Air Force Office of Special Investigations”:

http://en.wikipedia.org/wiki/U.S._Air_Force_Office_of_Special_Investigations

Wikipedia article: “Lincoln LaPaz”:

https://en.wikipedia.org/wiki/Lincoln_LaPaz

The emblem of the Air Force Office of Special Investigations (AFOSI) (wikimedia.org image)