Letter from Thomas gold to Mr Stephen Turk, Space Science adn Astrophysics, Institute for Plasma Research, Stanford University, Via Crespi, Stanford, California Encloses the latest version of the histogram of pulsar periods. Asks if he would suggest a good significance test for a bi-model distribution. Would be very important, suggesting that there is a class of pulsars tyhat are set up initially with slow rotation. 21 February 1973