text: For an infinite two-dimensional lattice, defined by its primitive vectors , its reciprocal lattice can be determined by generating its two reciprocal primitive vectors, through the following formulae,
  where  is an integer and
  Here  represents a 90 degree rotation matrix, i.e. a quarter turn. The anti-clockwise rotation and the clockwise rotation can both be used to determine the reciprocal lattice: If  is the anti-clockwise rotation and  is the clockwise rotation,  for all vectors . Thus, using the permutation
  we obtain
  Notably, in a 3D space this 2D reciprocal lattice is an infinitely extended set of Bragg rods&mdash;described by Sung et al.