The same natural relationship applies to 1,001; 2,002; 3,003; 4,004; 5,005; 6,006; 7,007; 64,100; 65,101; 66,102; 67,103; and 68,104.
Pausanias, Periégésis tés Hellados, 3,3,1; 3,3,2; 4,7,6 – 9; 4,6,4; 4,10,3; 4,15,3; 4,16,6.