Definite Article

First, marketing specialists must conduct research into a variety of different retailers to locate the best company or companies to which they can sell their products. Once that relationship has been established, both marketer and retailer will work together to research the best promotional tactics for the product.

Why is there no article before marketer and retailer? 'both marketer and retailer will work together...'

Should it not be 'both the marketer and retailer' or 'both marketers and retailers...'

Thanks