Finding Max Value of Column in Multi-Dimesional Array

[Samir via Digitalmars-d-learn]

Is there a cleaner way of finding the maximum value of say the 
third column in a multi-dimensional array than this?
int[][] p = [[1,2,3,4], [9,0,5,4], [0,6,2,1]];
writeln([p[0][2], p[1][2], p[2][2]].max);
I've tried the following
writeln([0, 1, 2].map!(p[a][2]).max);

but get an "Error: undefined identifier a" error.

I know there doesn't seem to be much of a difference between two 
examples but my real-world array is more complex which is why I'm 
looking for a more scalable option.

Thanks
Samir