Complex sentence: The classification was for a time considered very bold and speculative, especially in his proposal of a Nilo-Saharan language family, but is now generally accepted by African historical specialists and has been used as a basis for further work by other scholars.
Split into simpler sentences: The classification was for a time considered very bold and speculative, especially in his proposal of a Nilo-Saharan language family, but is now generally accepted by African historical specialists. It has been used as a basis for further work by other scholars.