Halvorson, Halvor Orin, 1897- Spores, a symposium held at Allerton Park, Illinois, October 11-12, 1956, [electronic resource] / under the auspices of the University of Illinois and with the support of the Office of Naval Research.. — Washington, : American Institute of Biological Sciences,, 1957 [c1958]. — x, 164 p. : ill. — (American Institute of Biological Sciences. Publication,) no. 5. - American Institute of Biological Sciences. Publication ; no. 5. .