(англ.)Calculating area enclosed by arbitrary polygon on earths surface. Approximated by integrating latitudinal strips with area of R² (L1-L2)(cos(A)dA) from 30° to 65° latitude; where R = 3889 km, A is latitude, and angles expressed in radians. Архів оригіналу за 12 Листопада 2020. Процитовано 23 Червня 2014.
(англ.)Calculating area enclosed by arbitrary polygon on earths surface. Approximated by integrating latitudinal strips with area of R² (L1-L2)(cos(A)dA) from 30° to 65° latitude; where R = 3889 km, A is latitude, and angles expressed in radians. Архів оригіналу за 12 Листопада 2020. Процитовано 23 Червня 2014.