DECLARE @mystring varchar(255)
		      SET @mystring = COALESCE(@mystring+',' , '') + CData.value('(/fields/Authors)[1]', 'varchar(255)') 
 CData field has these values <fields>
  <ReqDate>1/28/2014</ReqDate>
  <ReqLibrary>Main</ReqLibrary>
  <Authors>Robb, King, Saul</Authors>
</fields>