NMR references for fictitious spin-1/2

1. G. B. Furman, S. D. Goren, V. M. Meerovich, and V. L. Sokolovsky
   Fictitious spin-1/2 operators and correlations in quadrupole nuclear spin system,
   Int. J. Quantum Inf. 16, 1850008-19pp (2018).
   Abstract
2. S. Vega
   Multiple quantum cross-polarization NMR on spin systems with I = 1/2 and 3/2 in solids,
   Phys. Rev. A 23, 3152-3173 (1981).
   Abstract
3. S. Vega and Y. Naor
   Triple quantum NMR on spin systems with I = 3/2 in solids,
   J. Chem. Phys. 75, 75-86 (1981).
   Abstract
4. S. Vega
   Fictitious spin 1/2 operator formalism for multiple quantum NMR,
   J. Chem. Phys. 68, 5518-5527 (1978).
   Abstract
5. A. Wokaun and R. R. Ernst
   Selective excitation and detection in multilevel spin systems: Application of single transition operators,
   J. Chem. Phys. 67, 1752-1758 (1977).
   Abstract
6. S. Vega and A. Pines
   Operator formalism for double quantum NMR,
   J. Chem. Phys. 66, 5624-5644 (1977).
   Abstract