It's the tough matter found in whole grains, nuts, and fruits and veggies (specifically in the stalks, skins, and seeds) that doesn't dissolve in water. (health.com)
Indie book pricing is a tough matter because each book and each genre will sell differently at different price points. (selfpublishingreview.com)
Buying a house in the Bay Area is a tough matter, and it might make sense to match assets and liabilities. (alephblog.com)