Referencing Resources between CloudFormation stacks

If I have two cloudformation stacks, how do I references a resource in one stack from the other stack?

In the example below I have a stack that creates an EBS volume and want to reference that via the Ref: key in the second stack for my EC2 instance but I keep getting a rollback since it can't see that resource from the first stack:

"Template format error: Unresolved resource dependencies"

I already tried the DependsOn clause but it didn't work. Do I need to pass information via Parameters?

{
  "AWSTemplateFormatVersion": "2010-09-09",
  "Resources": {
    "CubesNetworking": {
      "Type": "AWS::CloudFormation::Stack",
      "Properties": {
        "TemplateURL":     "http://ift.tt/1J4MtMa"
      }
   },
   "CubesInstances": {
     "DependsOn": ["CubesNetworking"],
      "Type": "AWS::CloudFormation::Stack",
      "Properties": {
        "TemplateURL": "http://ift.tt/1J4MtMc"
      }
    }
  }

}