| 521 / | HD | SYNTHETIC RESINS OR NATURAL RUBBERS -- PART OF THE CLASS 520 SERIES |
| * | DD | SYNTHETIC RESINS (Class 520, Subclass 1) {3} |
| 50 | DF | .~ CELLULAR PRODUCTS OR PROCESSES OF PREPARING A CELLULAR PRODUCT, E.G., FOAMS, PORES, CHANNELS, ETC. {27} |
| 155 | DF | .~.~ Cellular product derived from a -N=C=X containing reactant wherein X is a chalcogen atom {10} |
| 170 | DF | .~.~.~ With -XH reactant wherein X is a chalcogen atom {3} |
| 171 | | .~.~.~.~ -XH reactant contains a halogen atom |