Classification
539 - Modern physics
224
530 - Physics
25
333 - Economics of land & energy
12
621 - Applied physics
12
523 - Specific celestial bodies & phenomena
5
520 - Astronomy & allied sciences
4
541 - Physical chemistry
4
620 - Engineering & allied operations
2
500 - Natural sciences & mathematics
1
550 - Earth sciences
1
571 - Physiology & related subjects
1
601 - Philosophy & theory
1
650 - Management & auxiliary services
1