DOM Level 0:
DOM Level 1, a W3C Standard
DOM Level 2, a W3C Standard
DOM Level 3: Several specs:
Document Object Model (DOM) Level 3 XPath Specification Version 1.0
Document Object Model (DOM) Level 3 Load and Save Specification
Document Object Model (DOM) Level 3 Validation Specification
Document Object Model (DOM) Level 3 Views and Formatting Specification
Document Object Model (DOM) Level 3 Events Specification Version 1.0