User:Juan Marquez

$\Sigma \subset M^3$

$O_1\cong S^1\times S^1$

$O_2=O_1\# O_1$

...

$O_g=O_{g-1}\# O_1$

$N_1=M\ddot{o}\cup D^2$

$N_2=N_1\# N_1$

...

$N_k=N_{k-1}\# N_1$

$M\ddot{o}\times S^1$

$N_2\stackrel{\sim}\times I^O$

$O_1\times S^1$