Pioneer application of efficiency engineering principles to hospital administration, made over a two year period. Codman was responsible for the “end result idea”. This revolutionary concept, which seems so obvious today, was that a hospital should follow every patient it treats long enough to determine whether or not the treatment was successful. If the treatment was not successful the cause of failure should be determined in order to prevent similar failures in the future. Codman was exceptionally outspoken in his views. Digital facsimile from Google Books at this link.
Codman first presented this paper publicly on May 20, 1914 at the 39th annual meeting of the American Gynecological Society. It was later published by the Society as "Study on hospital efficiency as represented by product," Trans. Amer. Gyn. Soc., 39, 60-95. Digital facsimile from Google Books at this link. Codman was undoubtedly aware that his contributions to efficiency in hospital administration needed to reach an audience far wider than the limited readership of the American Gynecological Society. He did not wait for the printed version of that lecture to appear in the society's journal. Instead, he had the text privately printed in Boston with the date May 10, 1914 (10 days before he presented his paper). The privately printed version was entitled A study in hospital efficiency as demonstrated by the case report of the first two years of a private hospital. This version had 27,  pp. and appeared in printed wrappers. It was printed by Thomas Todd Co., Boston. This version may be considered the first edition.
Codman next issued this work in the form of an expanded 43-page undated pamphlet in 1915 or 1916. For this version, which may be considered a second edition, Codman revised the title slightly to read Study in hospital efficiency: As demonstrated by the case report of the second two years of a private hospital. Boston: Privately Printed, 1915. The printed text is dated October 19,1915 on the last leaf. Digital facsimile from the Hathi Trust at this link.
Codman expanded and reissued this work in an undated third edition, changing the title to read A study in hospital efficiency: As demonstrated by the case report of the first five years of a private hospital. That edition, expanded to 179pp., contained references through January 1918 (p. 68). Digital facsimile of the 1918 edition from the Internet Archive at this link. A brief review of it was published in the Boston Medical and Surgical Journal, CLXXVIII, No., 4, 125 (January 24, 1918). When this third edition was published it contained a tipped-in slip reading:
“This Report will be sent gratis to any member of the American College of Surgeons or to any member of the Massachusetts Medical Society. To others the price will be one dollar. When you are through with this copy, kindly hand it to some other person—preferably to a Hospital Trustee.”
Codman died in 1940. After his death copies of the third edition were distributed in a blue cloth binding with a printed label pasted to the inside of the front cover. That label reads:
“This book is sent to you as an officer of the Massachusetts General Hospital, in fulfillment of a special request made by Dr. Codman shortly before his death on November 23rd, 1940.”
Because Codman's ideas became known mainly through his privately printed versions, one or more of those privately printed, and difficult to cite versions, rather than the journal publication, are nearly always cited.
(Thanks to Malcolm Kottler for unraveling the order of Codman's publications of his "end result idea.")