GB/T 12010.11-1989
Determination for sodium hydroxide contents of polyvinyl alcohol resins
ISO 1897-4:1977
Phenol, o-cresol, m-cresol, p-cresol, cresylic acid and xylenols for industrial use — Methods of test — Part 4: Visual test for impurities insoluble in sodium hydroxide solution (Excluding cresylic acid and xylenols)