{Sofia, University of; South Carolina, University of; Leland Stanford Junior University Library; Stanford University Press [Jessie Denton Whittern]; Staveley & Co.; William H. Steavenson; G. E. Stechert & Co.; Morton Stern; Elizabeth Ellen Sternberg [Mulders]; R. Sternberk; Steward Observatory}
{Clem Stoeckle; Julius F. Stone; P. W. Stoner; Clarence Strachauer; Samuel Wesley Stratton; George L. Streeter; Paul Stroobant; Georg Struve; Sunset Press; Sun Yatsen University Observatory; Swarthmore College Library; Eugene Swarzwald; Synchronome Co., Ltd}
{Barthet's Laboratory & Observatory; Raymond Bartholomew; William H. Barton, Jr.; Bautzen Observatory; Ernest H. Beattie; Wilhelm Becker; Otto Behrens; Belgium, Royal Observatory of; S. Beljawsky; Bell System Technical Journal; F. A. Bellamy; Andrew P. Beltran; Raine Bennett; Junior B. Benton; Berlin University Observatory; E. Bianchi; Claude R. Bird; Raymond Thayer Birge; Charles Bittinger; Vilhelm Bjerknes; Philip E. Bliss}
{Pacific Electric Railway Co. [incl to/from GEH]; Pacific Geographic Society [Humphrey Read]; Pan American Scientific COngress [José J. Bravo]; Paris Observatory; Const. Parvule; J. Newton Parker; Sir Charles Parsons; Pasadena Association; Pasadena High School and Junior College [Ida E. Hawes]; Pasadena Vocation Bureau [Marion de Paar]; A. W. Pawlow; Fred Pearson; Peckham Bros.; George B. Pegram; Walter M. Pegram; Peking Central Observatory; G. Edward Pendray}
{Albert Chase McArthur; Macbeth Daylighting Co., Inc. [Norman Macbeth]; Lucena McBride; Phoebe Merl McClees [ltrs M. E. Churchill ?? FHS; FHS ? Fisk Teachers' Agencies]; Frank McCoy; E. C. MacDowell; Anita Newcomb McGee; McGill University; Dean B. McLaughlin; MacMillan Co. Publishers [Rose Levy]; Mrs. John McMillan; Maud W. Makemson; E. Mallinckrodt, Jr.; Marburg University Library; Marchaut Calculating Machine Co. [folded]; W. L. Marcy; Marina, Instituto y Observatorio de; Marquis, A. N. & Co.}
{Ukrainian SSR Academy of Sciences; USSR Society of Cultural Relations with Foreign Countries [E. Tsubina; I. Korinetz; M. Apletin; E. Leite; M. Milikovsky]; US Civil Service Commission; US Coast and Geodetic Survey; US Customs Service; US Department of Commerce; US Geological Survey; US Naval Observatory; US Shipping Board; US Weather Bureau; Universal Film Manufacturing Co. [M. G. Jonas]; Université Libre de Bruxelles [R. Sedeyn]; University of California at Los Angeles [Frederick C. Leonard]; University of Utah [Junius J. Hayes]; University of Washington Library [W. E. Henry]; Universum Book Export Co., Inc.}
{Salto Observatory; Sanborn, Vail & Co.; San Diego Business and Professional Women's Club; San Diego County Planning Commission; San Diego Scientific Library; E. Sanger-Sheppherd; W. W. Sargeant; A. P. Saunders; Frederick A. Saunders; George G. Saunders}
