Apple continues to garner support for its iPad, set to be launched on the 3rd of April next.

It has signed up two additional publishers to its stable - book distributor Perseus Books Group and Workman Publishing Company, according to a report in the New York Times.

Workman publishes novels, cookbooks, and other titles. Perseus is an independent publisher that also distributes a number of books and titles from Harvard Business School Press and Zagat, the NYT said.

Sales of the iPad have apparently been brisk and Apple is set to coin it by nabbing a 30 percent commission for every sale it makes.

But Apple may find itself being challenged by its competitors such as Amazon because it won't let outlets sell books lower than it sells them in its iBookstore.

That means that Amazon will face visits from its publishers to renegotiate deals to match the deals they've made or may make with Apple.