• Techniques for forming ... are well established .
• This principle has been securely ( or firmly ) established by experiment.
• Techniques for forming ... are well established .
• This principle has been securely ( or firmly ) established by experiment.
Циммерман М., Веденеева К.. Русско-Английский научно-технический словарь переводчика. Russian-English scientific dictionary for translators. 2012