John Larkin, Professor in the Department of History at the State University of New York, Buffalo, wrote of them in his book "The Pampangans".  Chapter 2, "From Datus Descended" is excerpted as follows:

     "In spite of some scanty evidence of late Neolithic culture in Pampanga, there is no proof that settlement was continuous from that time onward.  Indeed, a mysterious gap exists between 1500 B.C. and 900 A.D., and the discovery of burial sites in Porac containing Chinese pottery from the late T'ang, Sung, Yuan, and Ming periods would indicate only that Pampanga harbored settlements from the late ninth or early tenth century.²
   The use of Chinese pottery, which lingered into the early years of the Spanish regime, suggests long-standing links between Pampanga and the outside world, whether with nearby regions or directly with Chinese merchants plying the Philippine coastal trade. ³  Nor did the Pampangans rely solely on such coastal contacts.  An early Spanish account concerning the Pampangans and the neighboring Tagalogs reported that they are keen traders, and have traded with China for many years, and before the advent of the Spaniards, they sailed to Maluco, Malaca, Hazian [Acheh?], Parani [Patani?], Burnei, and other kingdoms.⁴