 Many trade goods are mentioned in the Periplus, but some of the words naming trade goods are seen nowhere else in ancient literature, and so we can only guess as to what they might be.
<clarity>  Many trade goods are mentioned in the Periplus, but some of the words naming trade goods are seen nowhere else in ancient literature, and so we can only guess as to what they might be.
 Many trade goods are mentioned in the Periplus, but some of the words naming trade goods are seen nowhere else in ancient literature, leading to guesswork as to what they might be.