Category	Predictor(s)	Model label	Model form
I	D	M1	$a_{1} {(D^{2})}^{b_{1}}$
II	D, H	M2	$a_{2} {(D^{2} H)}^{b_{2}}$
II	D, H	M3	$a_{3} H {(D^{2})}^{b_{3}}$
III	D, ρ	M4	$a_{4} {(D^{2} ρ)}^{b_{4}}$
III	D, ρ	M5	$a_{5} ρ {(D^{2})}^{b_{5}}$
IV	D, ρ, H	M6	$a_{6} {(D^{2} ρ H)}^{b_{6}}$
IV	D, ρ, H	M7	$a_{7} ρ {(D^{2} H)}^{b_{7}}$