Friis-Christensen, E., & Wilhjelm, J. (1974). Polar CAP geomagnetic activity chart: Part A, Northern polar Cap, January-June 1968. Det Danske Meteorologiske Institut.
Chicago Style (17th ed.) CitationFriis-Christensen, Eigil, and J. Wilhjelm. Polar CAP Geomagnetic Activity Chart: Part A, Northern Polar Cap, January-June 1968. Kobenhavn: Det Danske Meteorologiske Institut, 1974.
MLA (9th ed.) CitationFriis-Christensen, Eigil, and J. Wilhjelm. Polar CAP Geomagnetic Activity Chart: Part A, Northern Polar Cap, January-June 1968. Det Danske Meteorologiske Institut, 1974.
Warning: These citations may not always be 100% accurate.
