"Print on demand" technologies, which make it doable to print as number of as a person book at a time, have made self-publishing (and vanity publishing) easier and more affordable, and it has permitted publishers to keep minimal-selling books in print instead than declaring them out of print. After https://buy-now.cognitiveinstituteofdallas.org/product-detail-listen-in-whff-radio-tuesdays-8pm-est.html