The reference in the given statement, "They are people of yellow complexion, oblique eyes, high cheekbones, sparse hair and medium height," is to the Mongoloids.

Mongoloids are one of the major racial groups and are characterized by specific physical features such as a yellowish complexion, oblique eyes, high cheekbones, sparse hair, and medium height. This racial group includes populations from various regions, including East Asia, Southeast Asia, and parts of Central Asia.

It`s important to note that racial classifications can be complex and sensitive, and there is often significant diversity and overlap within and between racial groups. Additionally, it is crucial to approach discussions about race and ethnicity with respect and avoid generalizations or stereotypes.