The complete text of Nandikeswara’s Abhinayadarpanam translated into English by Dr. Manomohan Ghosh can be accessed online at the Online Universal Library( Internet Archive).
Most dance schools teach their theory based on this text.
URL: http://www.archive.org/details/abhinayadarpanam029902mbp
Here you may either read the text online or download as PDF/for kindle etc.
Bharathanatyam and the worldwide web 