Explanatory notes
… include compounds of hydrogen with the following elements : oxygen ( headings 22.01 , 28.45 , 28.47 and 28.53 ), … combinations of nitrogen with the following elements : oxygen ( heading 28.11 ), halogens ( heading 28.12 ), … cover combinations of silicon with the following elements : oxygen ( heading 28.11 ), halogens ( heading 28.12 ), …