By Carolyn Cohn LONDON (Reuters) – Three years ago, a trip to the Southern Kenya production facilities of Canadian company Africa Oil attracted only seven potential investors. The investor trip, described by sales staff at Citi following a recent client conference, is just one illustration of the swelling interest in the most esoteric frontier markets. In a world of low yields and paltry growth, the attraction of frontier markets – the lesser developed emerging markets in Africa, Asia, Europe, the Middle East and Latin America – is pretty clear. “Everyone and his dog seems to know something about (frontier markets) now,” Citi wrote.