Following several threads on SO and aws forums, I am trying to get a basic nested cloudformation example working.

The `ChildStack01` creates a VPC, then `ChildStack02` adds a subnet. but after trying several combinations I get the same type of error, `Output 'VpcID' not found in stack`

```
{
   "AWSTemplateFormatVersion": "2010-09-09",

    "Resources": {
       "ChildStack01": {
           "Type": "AWS::CloudFormation::Stack",
           "Properties": {
               "TemplateURL": "https://s3-eu-west-1.amazonaws.com/cf-templates-1u1ziwem31f87-eu-west-1/xxx",
               "TimeoutInMinutes": "60"

            }
       },
       "ChildStack02": {
           "Type": "AWS::CloudFormation::Stack",
           "Properties": {
               "TemplateURL": "https://s3-eu-west-1.amazonaws.com/cf-templates-1u1ziwem31f87-eu-west-1/yyy",
               "Parameters": {
                  "VpcId" : { "Fn::GetAtt" : [ "ChildStack01", "Outputs.VpcID" ] }
               },
               "TimeoutInMinutes": "60"
           }
       }
   }

```

I have tried adding a parameter with

```
"VPC" : {
      "Description" : "VPC ID",
      "Type": "AWS::EC2::VPC::Id"
    }

```

but then generates an error as there is no reference value for VPC listed in <http://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/intrinsic-function-reference-ref.html>

Is there a basic way to get the VPC-id after it has been created?

thanks
Art