Table 2. The adjacent information of 31 provinces or provincial municipalities.

S/N	Region	Adjacent information	S/N	Region	Adjacent information
1	Beijing	2, 3	17	Hubei	12, 14, 16, 18, 22, 27
2	Tianjin	1, 3	18	Hunan	14, 17, 19, 20, 22, 24
3	Hebei	1, 2, 4, 5, 6, 15, 16	19	Guangdong	13, 14, 18, 20, 21
4	Shanxi	3, 5, 16, 27	20	Guangxi	18, 19, 24, 25
5	Inner Mongolia	3, 4, 6, 7, 8, 27, 28, 30	21	Hainan	19
6	Liaoning	3, 5, 7	22	Chongqing	17, 18, 23, 24, 27
7	Jilin	5, 6, 8	23	Sichuan	22, 24, 25, 26, 27, 28, 29
8	Heilongjiang	5, 7	24	Guizhou	18, 20, 22, 23, 25
9	Shanghai	10, 11	25	Yunnan	20, 23, 24, 26
10	Jiangsu	9, 11, 12, 15	26	Tibet	23, 25, 29, 31
11	Zhejiang	9, 10, 12, 13, 14	27	Shaanxi	4, 5, 16, 17, 22, 23, 28, 30
12	Anhui	10, 11, 14, 15, 16, 17	28	Gansu	5, 23, 27, 29, 30, 31
13	Fujian	11, 14, 19	29	Qinghai	23, 26, 28, 31
14	Jiangxi	11, 12, 13, 17, 18, 19	30	Ningxia	5, 27, 28
15	Shandong	3, 10, 12, 16	31	Xinjiang	26, 28, 29
16	Henan	3, 4, 12, 15, 17, 27

Note:

The numbers of provinces or provincial municipalities in this paper are in the order of Table 2.