text: Geographical association , as in northern ( å -- æ , bÄ iquÃ n ) and southern ( å -- æ , nÃ nquÃ n ) , is another popular method of categorization .
simplified: They are also often classed according to region , that is northern ( å -- æ , bÄ iquÃ n ) and southern ( å -- æ , nÃ nquÃ n ) .