| 700 / | HD | DATA PROCESSING: GENERIC CONTROL SYSTEMS OR SPECIFIC APPLICATIONS |
| 90 | DD | SPECIFIC APPLICATION, APPARATUS OR PROCESS {16} |
| 266 | DD | .~ Chemical process control or monitoring system {6} |
| 271 | DD | .~.~ Refinement or purification or rejuvenation {1} |
| 272 | | .~.~.~ Of fuel |