Table 1.

Indices for network-based approaches.

Method	References	Index	Length of path
CN (Common neighbor)	Newman (2001)	CNij = |Γi⋂Γj|	l = 2
JC (Jaccard index)	Jaccard (1912)	$J{C}_{ij}=\frac{|{\Gamma }_i\bigcap {\Gamma }_j|}{|{\Gamma }_i\bigcup {\Gamma }_j|}$	l = 2
LHN (Leicht-Holme-Newman)	Wang et al. (2015)	$LH{N}_{ij}=\frac{|{\Gamma }_i\bigcap {\Gamma }_j|}{k_i*k_j}$	l = 2
AA (Adamic-Adar)	Adamic and Adar (2003)	$A{A}_{ij}={\sum }_{z\in {\Gamma }_i\bigcap {\Gamma }_j}\frac{1}{log{k}_z}$	l = 2
PA (Preferential attachment)	Barabâsi et al. (2002)	PAij = ki*kj	Other
RA (Resource allocation)	Zhou et al. (2009)	$R{A}_{ij}={\sum }_{z\in {\Gamma }_i\bigcap {\Gamma }_j}\frac{1}{k_z}$	l = 2
LP (Local path)	Lü et al. (2009)	$L{P}_{ij}={\left[A^2+\beta A^3\right]}_{ij}$	l = 2, 3
Katz	Katz (1953)	$Kat{z}_{ij}={\left[\beta A+{\beta }^2{A}^2+\dots \right]}_{ij}$	l = 1, 2, …