Natyashastra
रङ्गे विकृष्टे भरतेन कार्यो गतागतैः पादगतिप्रचारः । त्र्यश्रस्त्रिकोणे चतुरस्ररङ्गे गतिप्रचारश्चतुरस्र एव ॥ २०॥
On an oblong stage, Bharata should perform elaborate footwork with going and turning steps, while on a triangular stage the footwork should be of the Tryasra type, and on a square stage, the footwork should be of the Caturasra type.
english translation
raGge vikRSTe bharatena kAryo gatAgataiH pAdagatipracAraH । tryazrastrikoNe caturasraraGge gatipracArazcaturasra eva ॥ 20॥
hk transliteration by Sanscript