https://mindwires.com/wp-content/uploads/2020/06/mindwireslrg-whitepad.png00Phil Hillhttps://mindwires.com/wp-content/uploads/2020/06/mindwireslrg-whitepad.pngPhil Hill2015-03-27 00:00:002020-11-20 13:35:50Postscript on Student Textbook Expenditures: More details on data sources