1. Adarsh (2021). Types and Materials for Water Piping. What Is Piping. https://whatispiping.com/water-piping/#:~:text=Water%20Pipes%20come%20in%20several%20types%20and%20sizes,of%20plastic%20pipes%20used%20in%20water%20piping%20systems
2. Aisyah, R. (2019). Indonesia’s Services Sector Has Great Potential, Trade Ministry Says. The Jakarta Post. https://www.thejakartapost.com/news/2019/01/20/indonesias-services-sector-has-great-potential-trade-ministry-says.html
3. Ajero, M. A. (2000). Future Emissions of Metro Manila.
4. Alave, K. (2011). Metro Manila Produces a Fourth of Philippine Garbage. Philippine Daily Inquirer.
5. Ann, C. (2015). Your Letters: Clean Water Problem in Jakarta. The Jakarta Post. https://www.thejakartapost.com/news/2015/03/04/your-letters-clean-water-problem-jakarta.html