Agricultural engineering as of January 1, 1933, 1934. From the atlas "Industry of the USSR at the beginning of the 2nd Five-Year Plan. Geographical atlas." - Conventional signs: boundaries (5 types), settlements (5 groups), railways (operating, under construction); industrial enterprises (16 types), the ratio of the area of ??arable land to the total territory of the region (4 gradations); numbers indicate the serial numbers of industrial enterprises in the list (Appendix: List of industrial enterprises to the Atlas. M., 1934).