What is the voltage across the circuit shown?
After seeing Horta's answer, I got another way to do it. 

Replacing each branch with its Norton's equivalent, we get



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Where,
$$I_x = \sum_{i=1}^{n}{\frac{V_i}{R_i}} \mathrm{\ \ and\ \ }R_x = R_1||R_2||\cdots ||R_n$$

And hence voltage between \$1\$ and \$0\$,
$$V_{1,0} = R_x\times I_x = R_x \times \sum_{i=1}^{n}{\frac{V_i}{R_i}}$$