January 1971, page 68—Title of the book reviewed at the bottom of the page should read: “Introduction to University Physics, 2nd edition.” The author's name is Morgan, not Magan.Page 97, center column, line 25—The word “no” is extraneous; sentence should read: “The average duration of observation for the UNKNOWNS was longer than for the KNOWNS…”February 1971, page 56, right‐hand column—Number of pages in the third edition of theMcGraw‐Hill Encyclopedia of Science and Technologyis 11 000, not 1100.