John Muir (2015). “JOHN MUIR’S CALIFORNIA COLLECTION: My First Summer in the Sierra, Picturesque California, The Mountains of California, The Yosemite & Our National Parks (Illustrated): Adventure Memoirs, Travel Sketches, Nature Writings and Wilderness Essays”, p.698, e-artnow
Orison Swett Marden (2015). “ORISON SWETT MARDEN Premium Collection - Wisdom & Empowerment Series (18 Books in One Volume): Steps to Success and Power, How to Get What You Want, An Iron Will, Be Good to Yourself, Every Man A King, Keeping Fit, Prosperity – How to Attract It, Stepping-Stones To Fame And Fortune...”, p.277, e-artnow