[Proj] cs2cs with WGS72

[Naiara Pinto]

Hi all,

I am trying to use cs2cs to go from Lambert Azimuthal Equal Area to
Lat Long. I get a problem when I try to use the WGS72 datum:
>cs2cs +proj=laea +ellps=sphere +lat_0=45 +lon_0=-100 +x_0 =0 +y_0=0
+to +proj=latlong +datum=WGS72 -r <<EOF
> 0 0
> EOF
Using to definition: proj=latlong datum=WGS72
Rel. 4.4.9, 29 Oct 2004
<cs2cs>:
projection initialization failure
cause: unknown elliptical parameter name
program abnormally terminated

This works fine with WGS84 and NAD83. Does anyone have any ideas why
this happens?

Thanks,

Naiara.