However, establishing patterns of this type is difficult.
However, establishing patterns of this type is difficult. It requires
a large vocabulary in all the languages being compared, in order to find
enough cognates; and it also requires a deep knowledge of the grammar
of each of the languages, in order to see cognate relationships that might
be obscured by morphology and contextual phonological change -- and not
to be fooled into seeing false cognates where morphology or phonology
have created chance similarities.