found: Crossroads [SR] p1984:container (Mark Spoelstra)
found: Classic folk music from Smithsonian Folkways [SR] p2004:container (Mark Spoelstra) insert (b. 1940, Kansas City; currently lives in California; folksinger, song writer, and guitarist)
found: New York times, Mar. 10, 2007(Mark Spoelstra, 66, folk performer in 1960s; d. Feb. 25, 2007, Pioneer, Calif.)
found: Wikipedia, viewed April 17, 2018(Mark Spoelstra, birth name Mark Warren Spoelstra; born June 30, 1940, Kansas City, Mo., died February 25, 2007, Pioneer, Calif.; singer-songwriter and guitarist; in 1969, while living in Sonoma County, California, he formed the Frontier Constabulary with Mitch Greenhill and Mayne Smith; Spoelstra left to resume his solo career in 1970, the band continued as the Frontier)
found: Northwestern University Libraries, Berkeley Folk Music Festival archive, 1957-1970(Jade Muse folk music group to perform tonight in Palo Alto; Mark Spoelstra's new modern folk group Jade Muse; Palo Alto Times, Sept 1, 1967)