postscript
4 Errors In Determination ...
Abstract...
Acknowledgements...
Combining these and some other sources of error together, we obtain the
preliminary results for the clusters A2218 and A1413 shown in Table 1.
Both of these clusters are at 
, so we neglect the possible error that
could arise from using a value of 
different to 
.
Table 1: Preliminary values of 
for the clusters A2218
and A1413.
We note that although the gas properties are different in these two clusters,
the estimates of 
are consistent. These two clusters comprise part of an
X-ray luminosity limited sample, which will be independent of cluster
orientation. This sample will allow us to calculate an unbiased estimate of
from a direct physical method, with a robust error budget.