N. Sinpaisansomboon, P. Intanon, W. Rakwichian, and N. Kongsricharoern, “Development of Two-Stage Anaerobic Digesters for Biogas Production from Biodegradable Waste of Phitsanulok Municipal, Thailand”, J. Renew. Energy Smart Grid Technol., vol. 2, no. 2, pp. 73–83, Dec. 2014.