Creating a node with node reference field in REST Service

Hello. Our team is developing a web site.
During the implementation, we are facing on problem related to creating a node with node reference field.

The below is a part of json results when we request a node information using a REST service module.

"field_places":{"und":[{"nid":"8"},{"nid":"9"}]}

However, when we create a new node using a json query, the notation is not working.
For example, if "field_places":{"und":[{"nid":"12"},{"nid":"14"}]} uses again

-----------------------------------------
form_errors:
field_places][und][0][nid: 'Place Nodes: found no valid post with that title.'
field_places][und][1][nid: 'Place Nodes: found no valid post with that title.'
-----------------------------------------

are returned.

Anybody who know how to make a json query for creating a node with node reference field