(a) Torus κ on |$\mathcal {T}^3$| corresponding to a circle k on |$\mathcal {B}^2$| parallel to the (x, y) plane. The torus is generated by fibers c above points Q along the circle k. (b) Torus μ on |$\mathcal {T}^3$| corresponding to a circle m on |$\mathcal {B}^2$| with a diameter parallel to the z-axis. Again, the torus is generated by fibers c above points Q on m.