Columbia subject headings:
Incas--Communication.
Incas--Mathematics.
Indians of South America--Andes Region--Communication.
Indians of South America--Andes Region--Mathematics.
Quipu.
Harvard subject headings:
Incas--Communication.
Incas--Mathematics
Indians of South America--Andes Region--Communication.
Indians of South America--Andes Region--Mathematics.
Quipu.
Princeton subject headings:
Incas--Communication.
Incas--Mathematics.
Indians of South America--Andes Region--Communication.
Indians of South America--Andes Region--Mathematics.
Quipu.