coupling mechanism between upper level and low level jet

fiscal system at county level and township level

interaction between upper level and lower level

municipal level and county level

+-18-crown-6-2

12-crown-4

13-hexaaza-14-crown-4

15-Crown-5

18 crown 6

18Crown6

18-Crown-6

18-crown-6-ether

18-Crown-6-tetracarboxylic

24-Crown-8

30-Crown-10

37-Crown-10

4′-acetylaminobenzo[15]crown5

4-crown-4

4-crown-amides-based