What is the structure of Basic beryllium Nitrate (BBN)?

Basic Beryllium nitrate is a Covalent compound and has as unique structure like [Be4O(NO3)], containg six nitrate group. The more interesting structure of Basic Beryllium nitrate because the nitrate group act as indented ligand in forming a bridge  between two Be atoms.

How to basic beryllium nitrate is obtained from beryllium nitrates?

Their is a unique feature of Beryllium nitrate , on heating at low temperature (125℃) it give Basic Beryllium nitrate , nitrogen gas and oxygen gas but at high temperature (above 1000℃) it give same products like other bivalent nitrate salts.