High-Pressure Densities of 1-Alkyl-3-methylimidazolium Hexafluorophosphates and 1-Alkyl-3-methylimidazolium Tetrafluoroborates at Temperatures from (313 to 473) K and at Pressures up to 200 MPa Taguchi, R.; Machida, H.; Sato, Y.; Smith, R.L.; Journal of Chemical & Engineering Data 2009, 54, 22-27