Table 1.

Summary of models.

Model	Two-parameter models	References
2A		Ghose and Das [10], Dwivedi and Ghose [14], Howell and Stuck [11], Caminal et al. [15], Gan et al. [7]
2B		Humphrey et al. [16] Movagharnejad and Sohrabi [17]
2C		Wald et al. [18]
	Three-parameter models
3A		Fan and Lee [20]
3B		Huang [21]
3C		Holtzapple et al. [22]