  In 2007 H. Long-Guang and Z. Xian, [H. Long-Guang and Z. Xian, Cone Metric
Spaces and Fixed Point Theorems of Contractive Mapping, J. Math. Anal. Appl.,
322(2007), 1468-1476], generalized the concept of a metric space, by
introducing cone metric spaces, and obtained some fixed point theorems for
mappings satisfying certain contractive conditions. The main question was "Are
cone metric spaces a real generalization of metric spaces?" Throughout this
paper we answer the question in the negative, proving that every cone metric
space is metrizable and the equivalent metric satisfies the same contractive
conditions as the cone metric. So most of the fixed point theorems which have
been proved are straightforward results from the metric case.
