Cita APA (7a ed.)

Friis-Christensen, E., & Wilhjelm, J. (1974). Polar CAP geomagnetic activity chart: Part A, Northern polar Cap, January-June 1968. Det Danske Meteorologiske Institut.

Cita Chicago Style (17a ed.)

Friis-Christensen, Eigil, y J. Wilhjelm. Polar CAP Geomagnetic Activity Chart: Part A, Northern Polar Cap, January-June 1968. Kobenhavn: Det Danske Meteorologiske Institut, 1974.

Cita MLA (9a ed.)

Friis-Christensen, Eigil, y J. Wilhjelm. Polar CAP Geomagnetic Activity Chart: Part A, Northern Polar Cap, January-June 1968. Det Danske Meteorologiske Institut, 1974.