H. . Sembiring and M. . Br Karo, “Test the Capability of the Down Flow-Up Flow Combination Filter Rate Lead (PB), Iron (FE) and Manganese (MN) which are Contained on Water Well Drill Public Residential Still Village Ndokum Siroga I Subdistrict Intersection Four Regency Karo ”, ijmst, vol. 10, no. 3, pp. 2348-2354, Sep. 2023.