nucFreqs = {{0.2}{0.3}{0.2}{0.3}};
global kappa = 1.0;
nucMatrix =	{{*, t*kappa, t, t*kappa }
			{ t*kappa, *, t*kappa,	t }
			{ t, t*kappa, *, t*kappa }
			{ t*kappa, t, t*kappa, * }};
Model nucModel = ( nucMatrix, nucFreqs, 1 );
Tree nucTree = (A,((B,((C,D),(E,F))),((G,H),(I,J))));
GetString ( ModelString, nucModel, -1 );
fprintf ( stdout, ModelString, "\n" );