RINGSTED, J.; AMTRUP, F.; ASKLUND, C.; BAUNSGAARD, P.; CHRISTENSEN, H. E.; HANSEN, L.; JAKOBSEN, C.; JENSEN, N. K.; MOESNER, J.; RASMUSSEN, J.; REINTOFT, I.; ROLSCHAU, J.; STARKLINT, H.; THOMMESEN, N. and; VRANG, J. Author Information
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Ringsted et al. (1979) studied this question.