The primary assistance I can offer is proofing/editing for
authors whose mother tongue is not English.
Other areas of some knowledge, special interest and a degree of limited expertise, are:
Principles of organic food and fibre production, processing, certification, etc;
Nutrition (principles of unusual aspects);
Sustainability (broad principles);
Principles of primary production economics;
Broader principles of economics including globalisation and privatisation;
Philosophical principles (comparative and religious);
Principles of conversational idiom, national and trans-national.
The word principles appears in each line. Why? Simply put,
rules are for the guidance of the wise and the obeisance of fools.
Principles usually remain inviolable. Rules often
become obsolete as time and circumstances change.