5In Ref. [14], the relation b ⋅ = k⊥k⊥′sinβ is also introduced in addition to (??) and (??). However, it is fully equivalent to (??) and does not provide any additional information.
= k⊥k⊥′sinβ is also introduced in addition to (??)
and (??). However, it is fully equivalent to (??) and does not provide any additional information.