California Code
ARTICLE 2 - Definitions
Section 3635.5.

3635.5. “Tracts of land” means land areas under separate ownership which are all of the following:

(a) Contiguous either on the surface or in the subsurface.

(b) Located within a field which has been producing for more than 20 years.

(c) Located within a field over 75 percent of which lies within incorporated areas.

(Added by Stats. 1971, Ch. 1673.)