Abstract
We generate fixed three- and four-light-flavour sets of partons using MRST2004 partons
as input. We show that it is important to set nf = 3 in the strong coupling, as
well as in the splitting and coefficient functions, in order to obtain a consistent set of
fixed-flavour partons. We compare the description of data using partons in both variableand
fixed-flavour-number-schemes.