URL:https://www.researchgate.net/profile/Jeffrey_Steiner2/publication/43263350/figure/download/fig4/AS:447564706258947@1483719149287/The-relationship-between-latitude-and-21-June-day-length.png
掲載元:https://www.researchgate.net/figure/The-relationship-between-latitude-and-21-June-day-length_fig4_43263350