stata 用findit psmatch2 安装
显示：
connection timed out -- see help r(2) for troubleshooting
http://fmwww.bc.edu/RePEc/bocode/p/ either
  1)  is not a valid URL, or
  2)  could not be contacted, or
  3)  is not a Stata download site (has no stata.toc file).

各位大佬，该怎么破