Major nodes: ClassI | OR1/3/7 | OR2/13 | OR2M/T/V | OR4/12 | OR5/8/9 | OR5A/AN | OR6/10/11 | OR10D/G/S | OR14 | OR51/52 | Schiff6↰
────────────────────────────────────────────┬───┬────── OR51Q1
│ └───┬───┬────── OR51A2
│ │ └────── OR51A4
│ └────── OR51A7
└────── OR51L1
