Africa
(There are no railways in Central African Republic, Chad, Niger)
Asia
Australasia
Europe
North America
South America & Central America
See also: Transportation by country, Lists_of_companies
... \begin{matrix} f_j & = & \sum_{k=0}^{\frac{n}{2}-1} x_{2k} e^{-\frac{2\pi i}{n} j(2k)} + \sum_{k=0}^{\frac{n}{2}-1} x_{2k+1} e^{-\frac{2\pi i}{n} j(2k+1)} ...