00001 ~ 00999   Logic
00500 ~ 00599     Logical Fallacies

01000 ~ 09999   Mathematics
01400 ~ 01999     Set Theory
02000 ~ 02999     Unit Conversion Equations
02000 ~ 02099       Mass & Weight
02100 ~ 02199       Length & Distance
02200 ~ 02299       Volume
02300 ~ 02399       Time
02400 ~ 02499       Luminosity

10000 ~ 19999   Computer Science

20000 ~ 29999   Physics

30000 ~ 39999   Chemistry