  From the observing campaigns of a number of helioseismic telescope networks
such as the Global Oscillation Network Group (GONG) and also from the Solar
Heliospheric Observatory satellite (SoHO), helioseismologists now have data on
in excess of 20000 oscillation frequencies of the modes known collectively as
the 5 minute oscillations. Depending on the order and degree of the modes these
data are available either as individual frequencies of modes with known radial
order n, spherical harmonic degree l, and order m, or as so-called
`a-coefficients' which are obtained by fitting polynomials to ridges of power
in the (l,\nu) diagram. Although there is a one-to-one relationship between
these two types of data, the conversion between them is not straightforward
which complicates comparison of helioseismic inference between the two types of
data. Their relationship with each other and with the solar rotation rate is
clarified in this paper.
