Khaodee, Warangkhana, Ratikon Wongkiti, & Suphatta Madang. " The Application of Using Natural Reagent Extracted from Purple Sweet Potato for Naked-Eye Detection of Copper in Water Samples." Naresuan University Journal: Science and Technology (NUJST) [Online], 26.3 (2561): 181-188. Web. 1 Jun. 2020