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| Ordovician period; Ordovician age (MichaelBurov); Ordovician time (MichaelBurov); the Ordovician (MichaelBurov); Ordovician (геол. MichaelBurov) | |||
| Ordovician system | |||
| the Ordovician (второй период палеозойской эры) | |||
| Ordovician | |||
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ордовик : 23 a las frases, 4 temas |
| Estratigrafía | 5 |
| Geocronología | 4 |
| Geología | 13 |
| Makárov | 1 |