REST Query problem - RetrieveMultiple with $filter

Hi all,

I am working in CRM 2011 Online with JQuery and REST Endpoint. I want to retrieve multiple records from "CampaignResponseSet".

My query:
https://{domain}/XRMServices/2011/OrganizationData.svc/CampaignResponseSet?$filter=Subject eq 'Krátký, Štěpán - 10.1.2013 11:23'.

Campaign response record with subject 'Krátký, Štěpán - 10.1.2013 11:23' already exists but result of request is null.

Could anyone help me?