1. A sensitive pyramidal-diamond tool for indentation measurements;Knoop,1939
2. The measured Knoop hardness of hard substances and factors affecting its determination;Thibault;Trans. A.S.M.,1947
3. Indentation Hardness Testing;Lysaght,1949
4. Use of a two diagonal measurement method for reducing scatter in Knoop microhardness testing;Blau;Scripta Met.,1980