In addition to the magazine listed above, there is also the January 1987 Model Railroading, USRA  Single-Sheathed 40-foot Box Cars (introduced as part 1 of the History of America's Steel Framed Box Cars) pages 9 through 15.  Also written by Richard Hendrickson, with assistance by Al Westerfield  - for additional reading and a roster listing of the USRA cars. 

Richard notes that he is indebted to James E Lane's "comprehensive and extensively researched article" USRA Freight Cars,  Railroad History  No. 128, Spring 1973. (R&LHS Inc)
   Also credits Al Westerfield. 
                                                                                                                                                                                                                                                  Jim Dick - Roseville, MN