1. Reinitzer, F., Monats. Chem., 1888, 9, 421.
2. Flory, P.J., Proc. R. Soc., 1956, A234, 73.
3. Kwolek, S.L., British Patent 1283064, 1968 ( E.I. DuPont de Nemours and Co.).
4. Goodman, I., McIntyre, J.E. & Stimpson, J.W., British Patent 989552, 1962 (Imperial Chemical Industries).
5. Goodman, I., McIntyre, J.E. & Aldred, J.H., British Patent 993272, 1962 (Imperial Chemical Industries plc.).