One can still encounter the old classification in many manuals and on most websites.

However, the older classification better reflects the evolutionary relationships between the genera.

The older and somewhat more complex classification is still used in some programs, especially for clinical research studies.

They retained their old classification and continued in service up to early 1970s.

A very old classification that is sometimes still seen is:

A very old classification that is sometimes still seen had them in:

That was real progress because old classifications were highly arbitrary and had harmful effects on wild animals.

Textbooks and other sources produced in the last century are inevitably based on older classifications.

None of the old classifications will fit them.

An older clinical classification, based on pioneering work by Fischer in 1938, is mainly of historical significance.