"Topic Snapshot: Natural Organic Material," American Water Works Association Research Foundation, 2007, 22 Apr, 2007 <存档副本. [2011-08-31]. (原始内容存档于2007-09-28).>.
"Topic Snapshot: Natural Organic Material," American Water Works Association Research Foundation, 2007, 22 Apr, 2007 <存档副本. [2011-08-31]. (原始内容存档于2007-09-28).>.