Columbia subject headings:
Harvard subject headings:
Birds--Eggs.
Birds--Embryology.
Eggs--Incubation
Embryology--Reptiles.
Reptiles--Eggs
Reptiles--Embryology.
Princeton subject headings:
Birds--Development.
Birds--Eggs--Incubation.
Birds--Embryology.
Eggs--Incubation.
Embryology--Reptiles.
Reptiles--Development.
Reptiles--Eggs--Incubation.