It was my error and the duplicate could have been identified and deleted.
However:
The National Archives has relinquished Crown Copyright on documents within its control provided certain conditions are met. Basically you are required to include (a) an acknowledgement that the record is in the care of TNA (b) the full reference of the document.
In the case of a census entry
For 1841 this includes the class/piece/book number (e.g. HO107/1234/5), folio/schedule No. and page No.
For 1851-1901 this includes the class/piece number, folio/schedule No. and page No.
For 1911 this includes the Class/piece number and schedule No.
Fred