Dr. Athula Perera & Mr.Amitha Kumara සංයුක්ත ගණිතය - 2011 - 117p 1 - 2023-11-15 ISBN: 978-955-51413-4-5 Nat. Bib. No.: 0005226 Nat. Bib. Agency Control No.: PER Universal Decimal Class. No.: 510