NIST: Determinable rotational and centrifugal dist. const.

Kivelson-Wilson Parameters for planar molecules	Kirchhoff parameters (following Watson [15])	Watson parameters [16]

A′	A′′ = A′ - 1/2τ′_bbcc	A
B′	B′′ = B′ - 1/2τ′_aacc	B
C′	C′′ = C′ - 1/2τ′_aabb	C
τ_aaaa	τ_aaaa	Δ_J
τ_bbbb	τ_bbbb	Δ_JK
τ_abab	τ_cccc	Δ_K
τ_aabb	τ₁ = τ′_aabb + τ′_bbcc + τ′_ccaa	δ_J
τ_aabb	τ₂ = (A′ / S) τ′_bbcc + (B′ / S) τ′_aacc + (C′ / S) τ′_aabb	δ_K

^aFor conversion between the various sets of parameters see References [4], [9], [10], and [17].