1. (a) Meerwein, H.; Hinz, G.; Hofmann, P.; Kroning, E.; Pfeil, E. J. Prakt. Chem.
1937, 147, 257–285. (b) Meerwein, H.; Bettenberg, E.; Pfeil, E.; Willfang, G. J. Prakt. Chem.
1939, 154, 83–156.
2. Coll. Vol. V 1973, 1080. Triethyloxonium tetrafluoroborate. (b) Curphey, T. J. Org. Synth.
3. Coll. Vol. VI, 1988, 1019. Trimethyloxonium tetrafluoroborate.
4. (a) Meerwein, H. Org. Synth.; Coll. Vol. V 1973, 1080. Triethyloxonium tetrafluoroborate.
5. (b) Curphey, T. J. Org. Synth.; Coll. Vol. VI, 1988, 1019. Trimethyloxonium tetrafluoroborate.