| 552 / | HD | ORGANIC COMPOUNDS -- PART OF THE CLASS 532-570 SERIES |
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| * | DD | ORGANIC COMPOUNDS (Class 532, subclass 1) {11} |
| 208 | DF | .~ Polycyclo ring system containing anthracene configured ring system having at least one double bond between ring members and having oxygen single bonded or any atom double bonded directly at the 9- and 10-positions (e.g., anthraquinones, etc.) {19} |
| 221 | DF | .~.~ Sulfur bonded directly at beta position (i.e., 2-, 3-, 6- or 7-position) {4} |
| 225 | DF | .~.~.~ Nitrogen bonded directly at alpha position (i.e., 1-, 4-, 5- or 8-position) {2} |
| 228 | DF | .~.~.~.~ Additional ring containing {3} |
| 232 | DF | .~.~.~.~.~ Oxygen, sulfur, nitro or halogen bonded directly to the additional ring {1} |
| 233 |  | .~.~.~.~.~.~ Plural additional rings containing |