| 548 / | HD | ORGANIC COMPOUNDS -- PART OF THE CLASS 532-570 SERIES |
| * | DD | ORGANIC COMPOUNDS (Class 532, Subclass 1) {1} |
| * | DD | .~ HETEROCYCLIC CARBON COMPOUNDS CONTAINING A HETERO RING HAVING CHALCOGEN (I.E., OXYGEN, SULFUR, SELENIUM, OR TELLURIUM) OR NITROGEN AS THE ONLY RING HETERO ATOMS (Class 540, subclass 1) {4} |
| 954 | DF | .~.~ Hetero ring is three-membered including nitrogen and carbon {11} |
| 956 | DF | .~.~.~ Phosphorus attached directly or indirectly to the hetero ring by nonionic bonding {1} |
| 957 | | .~.~.~.~ Plural phosphori |