Run the following five regressions (excluding the data for Malta): Growth on (1) TradeShare and YearsSchool;
(2) TradeShare and ln(YearsSchool);
(3) TradeShare, ln(YearsSchool), Rev_Coups, Assassinations and ln(RGDP60);
(4) TradeShare, ln(YearsSchool), Rev_Coups, Assassinations, ln(RGDP60), and TradeShare×ln(YearsSchool);
and (5) TradeShare, TradeShare2, TradeShare3, ln(YearsSchool), Rev_Coups, Assassinations and ln(RGDP60).

请问给位大大，Growth (2) TradeShare and ln(YearsSchool)中， ln(YearsSchool)怎么去设置，或者含义是什么？