Columbia subject headings:
Ptolemy, active 2nd century. Almagest.
Ptolemy, active 2nd century. Optics.
Ptolemy, active 2nd century. Planetary hypotheses.
Harvard subject headings:
Ptolemy, active 2nd century. Almagest.
Ptolemy, active 2nd century. Hypotheses.
Ptolemy, active 2nd century. Optics.
Princeton subject headings:
Ptolemy, active 2nd century. Almagest.
Ptolemy, active 2nd century. Optics.
Ptolemy, active 2nd century. Planetary hypotheses.