Karl O Christe, David A Dixon, Douglas McLemore, William W Wilson, Jeffrey A Sheehy, Jerry A Boatz,
On a Quantitative Scale for Lewis Acidity and Recent Progress in Polynitrogen Chemistry Journal of Fluorine Chemistry. ,vol. 101, pp. 151- 153 ,(2000) ,
10.1016/S0022-1139(99)00151-7