Corrections

April 1971, page 20, right‐hand column—Reference 3 to the story on x‐ray parametric conversion should have included: I. Freund, B. Levine, Phys. Rev. Lett. 25, 1241 (1970).

May 1971, page 71—Our report on the award of a National Medal of Science to Allan Sandage failed to make clear the fact that the Hale Observatories are operated jointly by the Carnegie Institution of Washington and California Institute of Technology.

May 1971, page 59—Price of A Training Manual for Nuclear Medicine Technologists should read $1.75 ($0.95 in microfiche). It is available from the Superintendent of Documents, US Government Printing Office, Washington, D.C. 20402.

May 1971, page 64—The name of one of the members of the “Committee to Study the Fundamentals of Amorphous Materials” was misspelled. John Tauc should be corrected to read Jan Tauc.