| 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} |
| 213 | DF | .~.~ The polycyclo ring system and an additional polycyclo ring system having at least three cyclos are bonded directly to the same atom (e.g., plural anthracene configured ring systems bonded directly to the same sulfur, etc.) {1} |
| 214 | DF | .~.~.~ The atom is nitrogen (e.g., anthrimides, etc.) {3} |
| 216 |  | .~.~.~.~ The polycyclo ring system is tetracyclic |