The Vosk is a mighty river which flows westward, emptying into a vast rence delta, finding its way eventually to Thassa, the sea ...
- Slave Girl of Gor, pag 248 -

On river barges, for hundreds of pasangs, I had made my way down the Vosk, but where the mighty Vosk began to break apart and spread into its hundreds of shallow, constantly shifting channels, becoming lost in the vast tidal marshes of its delta, moving toward gleaming Thassa, the Sea, I had abandoned the barges, purchasing from rence growers on the eastern periphery of the delta supplies and the small rush craft which I now propelled through the rushes and sedge, the wild rence plants.
- Raiders of Gor, pag 5 -

The actual source of the tributary to the Vosk, now called the Thassa Cartius, as you know, was found five years later by the explorer, Ramus of Tabor, who, with a small expedition, over a period of nine months, fought and bartered his way through the river tribes, beyond the six cataracts, to the Ven highlands. The Thassa Cartius, with its own tributaries, drains the highlands and the descending plains.
- Explorers of Gor, pag 16 -