@Article{ PaoTam16, author = { Paolini, Emanuele and Tamagnini, Andrea }, title = { Minimal clusters of four planar regions with the same area }, journal = { ESAIM: COCV }, year = { 2018 }, doi = { 10.1051/cocv/2017066 }, volume = { 24 }, number = { 3 }, pages = { 1303-1331 }, URL = { http://cvgmt.sns.it/paper/3120/ }, note = { cvgmt preprint} }