Watthanaphap, Naruephon, et al. “DETERMINATION OF CHLORPYRIFOS IN LETTUCE (LACTUCA SATIVA L.) BY MICROWAVE-ASSISTED EXTRACTION COUPLED WITH HEADSPACE SINGLE DROP MICROEXTRACTION”. International Journal of Pharmacy and Pharmaceutical Sciences, vol. 9, no. 5, May 2017, pp. 248-55, doi:10.22159/ijpps.2017v9i5.16849.