Abeyadeera , Nilmini Geometry : 6 -11 - Samudara : Colombo ; 2023. - 355 p; 24 cm . 01 - 2025-01-10 ISBN: 9786242032160 Nat. Bib. No.: 0011089 Nat. Bib. Agency Control No.: ABE Universal Decimal Class. No.: 510