1971 House Internal Security Committee staff report. Publications During the 1960s and 1970s, the PLP published a magazine called Progressive Labor, which first appeared as a monthly before shifting to quarterly and later bimonthly publication. The press run of Progressive Labor circa 1970 was approximately 10,000. The party also published Challenge, a publication likewise issued at changing intervals over the years. In 1970, the press run of this publication was approximately 75,000, according to the estimates of government investigators, with many of these copies unsold.Challenge remains in production today as a biweekly, issued under the same covers with its parallel Spanish language counterpart Desafío. The PLP also produces a semiannual theoretical magazine, The Communist.During 1963 and 1964, the PLP also produced a theoretical magazine called Marxist-Leninist Quarterly. This publication was terminated and merged with Progressive Labor magazine in 1965. A West Coast publication called Spark was also produced from 1965 until early 1968. See also Bill Epton Worker Student Alliance Further reading Robert Jackson Alexander, Maoism in the Developed World. Westport, CT: Greenwood Publishing Group, 2001. Leigh David Benin, A Red Thread In Garment: Progressive Labor And New York City’s Industrial Heartland In The 1960s And 1970s. Ph.D. dissertation. New York University, 1997. Leigh David Benin, The New Labor Radicalism and New York City's Garment Industry: Progressive Labor Insurgents During the 1960s. New York: Garland Publishing, 1999. House Committee on Internal Security, Progressive Labor Party: Hearings Before the Committee on Internal Security, House of Representatives, Ninety-Second Congress, First Session: April 13, 14, and November 18, 1971 (Including Index). Washington, DC: U.S. Government Printing Office, 1972. Progressive Labor Party, "The History of the Progressive Labor Party – Part One," Progressive Labor, vol. 10, no. 1 (August–September 1975). D.S. Sumner and R.S. Butler (Jim Dann and Hari Dillon). The Five Retreats: A History of the Failure of the Progressive Labor Party. Reconstruction Press, 1977. Mary-Alice Waters, Maoism in the U.S.: A Critical History of the Progressive Labor Party. New York: Young Socialist Alliance, 1969. Historic PLP publications Bill Epton, The Black Liberation Struggle (Within The Current World Struggle). Speech at Old Westbury College, February 26, 1976. Harlem: Black Liberation Press, 1976. Bill Epton, We Accuse: Bill Epton Speaks to the Court. New York: Progressive Labor Party, 1966. Harlem Defense Council, Police Terror In Harlem. NY: Harlem Defense Council, n.d. [1964?]. [Wendy Nakashima], Organize! Use Wendy Nakashima's campaign for assembly (69 a.d.) to