  N. Doiron-Leyraud et al. in [1] report on the experimental observation of
small holes pockets in the energy spectrum of YBa2Cu3Oy (YBCO) coming below the
transition into the charge ordered (CO) phase as a result of a Fermi surface
(FS) reconstruction. We comment that their results seem to be more consistent
with a unidirectional charge density wave (CDW) vector direction of which
alternates along the c-axis between neighboring CuO2 -planes.
