I am writing a research review on dark matter and cosmology. I ran into a paper (see
arXiv) describing the problems faced by LCDM cosmology. One such problem related to the alignment of the low multipoles (as L. Perivolaropoulos puts it).
The exact phrase used in the paper is
The normals to the octopole and quadrupole planes are aligned with the direction of the cosmological dipole at a level inconsistent with Gaussian random, statistically isotropic skies at 99.7% (Copi et.al., 2010).

I am comfortable with the idea of octopoles and quadrupoles as higher order terms of the same multipole expansion that gives the dipole fields, but I do not understand what is meant by the plane of the quadrupole and octopole.
Can anybody help me to understand this?
cohen990