Complex sentence: New areas of study opened up in the field and were the subject of extensive empirical research giving rise to concepts such as the product-service spectrum, relationship marketing, franchising of services, customer retention, and others.
Split into simpler sentences: New areas of study in the field opened up and were the subject of extensive empirical research. This gave rise to concepts such as the product-service spectrum, relationship marketing, franchising of services, customer retention, and others.