Table 1.

Different models for Tikhonov Regularization and their corresponding penalty functions.

	Model	Penalty function
a)	Ridge	$\left|\right|J|{|}_2^2$
b)	LORETA	$\left|\right|LJ|{|}_2^2$
c)	LASSO	||J||1
d)	LASSO Fusion	||LJ||1
e)	MPLS	$\sum _k{\lambda }_k{\psi }_k(J)$
f)	Fused LASSO	${\lambda }_1\sum _{i=1}^{S-1}\left|\right|J_{i,·}|{|}_1+{\lambda }_2\sum _{i=1}^{S-1}||J_{i+1,·}-J_{i,·}|{|}_1$
g)	ENET	λ1||J||2+λ2||J||1
h)	ENETL	λ1||LJ||2+λ2||LJ||1
i)	Smooth LASSO	λ1||LJ||2+λ2||J||1
j)	MXN	$\left|\right|J|{|}_{p,q}={(\sum _{t=1}^T{(\sum _{i=1}^S|J_{i,t}{|}^p)}^{\frac{q}{p}})}^{\frac{1}{q}}$
k)	GLASSO	$\sum _{s=1}^S{(\sum _{t=1}^T|J_{i,t}{|}^2)}^{\frac{1}{2}}$
l)	ELASSO	$\sum _{t=1}^T{(\sum _{i=1}^S\left|J_{i,t}\right|)}^2$