| 521 / | HD | SYNTHETIC RESINS OR NATURAL RUBBERS -- PART OF THE CLASS 520 SERIES |
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| * | 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} |
| 174 |  | .~.~.~.~ -XH reactant contains a C-X-C group {3} |
| 175 | DF | .~.~.~.~.~> C-X-C reactant contains a carbohydrate group |
| 176 | DF | .~.~.~.~.~> With non -C-X-C- containing reactant |
| 177 | DF | .~.~.~.~.~> C-X-C reactant contains a carbocyclic ring, e.g., aromatic, etc. |