Books with title Too Many Aliens

Maktel Geebrit, Pleskit's pen pal from back home on Hevi-Hevi, is finally going to visit him on Earth. Pleskit is excited, but a little nervous, too. How will Maktel get along with Pleskit's new friend, Tim? And just how does a kid cope with having two best friends on the same planet, anyway? As if that question wasn't hard enough, Pleskit's Fatherly One also has an off-world visitor - an elegant trader named Ellico vec Bur. But is Ellico really a friend, or is the trader also a traitor . . . the greatest menace that the mission to Earth has yet faced? The search for an answer plunges Pleskit, Tim, Maktel, and Linnsy into danger beyond their wildest dreams!