1 Subjects: “...regional differences...”

2 Subjects: “...gender differences...”

3 Subjects: “...regional differences...”

4 Subjects: “...difference-in-differences model...”

5 Subjects: “...regional differences...”

6 Subjects: “...regional difference...”

7 Subjects: “...difference-in-differences...”

8 Subjects: “...spatial and temporal difference...”

9 Subjects: “...difference...”

10 Subjects: “...different research scales...”

11 Subjects: “...the microwave polarization difference index...”

12 Subjects: “...religious difference...”

13 Subjects: “...finite difference approximation...”