Along with Manu Garcia and Angelino, Thierry Ambrose has six goals in 20 appearances, while Paolo Fernandes, Pablo Mari and Thomas Agyepong have also contributed.
“They see that we have started working with their boys in the right way, that they have made physical and tactical steps, and that they perform every week," Vreven said.
“These players have developed so well, and so quickly. City value that, so they don't leave us out in the cold – the mutual respect is enormous.
“Let's not be vague – this cooperation is first of all a business deal.
“We get good players, make them even better, and then they return to City or are sold."