| 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} |
| 99 | DF | .~.~ Cellular product formation prior to or during solid polymer formation in the presence of a stated ingredient other than water {18} |
| 114 | DF | .~.~.~ Ingredient contains a -C-X-C- group wherein X is a chalcogen atom and none of the C atoms bonded to the chalcogen are double-bonded to an additional chalcogen atom {2} |
| 115 |  | .~.~.~.~ -C-X-C- compound contains a nitrogen atom |