PIE *gn- > know/ken

[Dennis Philps]

[ moderator re-formatted ]

Could anyone tell me at what stage in history the initial voiced consonant in
PIE roots such as *gno- "know/ken/can" or *gen- "knife", etc. became devoiced,
and why this devoicing concerns some roots (e.g. *gen- "knife", etc.) but not
others (e.g. *ghen- > "gnat"). Also, is it correct to state that English forms
such as "know" are derived from zero grade (*gno-), whereas "ken (dial.)/can"
are derived from the full (e) grade (*gen-)?  Could anyone provide me with any
references of papers etc. dealing with this type of evolution?

Many thanks,
Dennis Philps