and $a_ 1 = a_+=0$.

5.  $a_ - = 0$: $\left( {{b_ + } + {t_{13}}{b_1}{e^{ - i{\delta _{CP}}}}} \right){b_ - } = 0$ is required and ${{b_ + } + {t_{13}}{b_1}{e^{ - i{\delta _{CP}}}}} = 0$ is the solution because ${b_ - } = 0$ gives $\left| {{m_1}} \right| = \left| {{m_2}} \right|$ from Eq.(\[Eq:masses for IHseesaw\]). The remaining conditions are fulfilled by either ${a_ + } + {t_{13}}{a_1}{e^{ - i{\delta _{CP}}}} = 0$ or ${a_1} = {a_ + } = 0$. We obtain that ${a_ + } + {t_{13}}{a_1}{e^{ - i{\delta _{CP}}}} = 0$, ${{b_ + } + {t_{13}}{b_1}{e^{ - i{\delta _{CP}}}}} = 0$ and $a_ - = 0$ or that ${{b_ + } + {t_{13}}{b_1}{e^{ - i{\delta _{CP}}}}} = 0$ and ${a_1} = {a_ + } =a_ - = 0$.

All of the cases for IH are not independent. For instance, the case 5 is included in the case 2 or in the case 3 both with the additional condition of $a_-=0$.

[99]{} B. Pontecorvo, \[\];\
Z. Maki, M. Nakagawa and S. Sakata, . Y. Fukuda, et al. (Super-Kamiokande Collaboration), ; ;\
T. Kajita, .\
See also, T. Kajita and Y. Totsuka, . J.N. Bahcall, W.A. Fowler, 