Making your own hollow blocks. - University of the Philippines (Diliman) Institute of the Science and Mathematics Education Development (Quezon City Institute for Science and Mathematics Education Development, University of the Philippines, 1984)
"This one of a series of science modules prepared by the University of the Philippines, Institute for Science and Mathematics Education Development (ISMED) supported by the Educational Development Projects Implementing Task Force (EDPITAF)"
Keywords: Hollow bricks