E2003 undeclared identifier in other unit, delphi

I declare some records in one unit to use it in second. But seconde unit can't find it and give E2003, what's wrong?

'''

unit DataTypes;

interface

uses
   Vec;

implementation


  type TGeo = record                     
        Pos : T3DVector;
        R, Longitude, Latitude : real;
      end;

  type TKepEl = record                    
        Rp, e, ArgLat, PeriArg, RAAN, Incl : real;
     end;

  type TCartesian = record                
        Pos : T3DVector;
        Vel : T3DVector;
  end;

  type TOrbData = record                  
        Epoch : TDateTime;
        KepEl : TKepEl;
        Cart  : TCartesian;
        Geo   : TGeo;
  end;

''' That's first unit with record.

That's part of second, that use this records: '''

unit Mathem;

interface

uses
  Math,
  DateUtils,
  DataTypes,
  Vec;

function InitOrbit( AEpoch : TDateTime;
    ARp, Ae, AArgLat, APeriArg, ARAAN, AIncl : real ) : TOrbData; overload;

'''

TOrbData give an error