The ISTD Cecchetti videos are of the children’s work most of it being made up by teachers and are not Enrico Cecchetti’s exercises though they aim to follow his principles. Most of his class exercises are published in The Manual which is for sale from ISTD but fairly unreadable unless you already are familiar with the work! - The adage dedicated to his cat is rather lovely. - Other exercises have been passed down from his pupils, my teacher was taught by Enrico Cecchetti. Much of the Cecchetti method is also recorded in both Laban & Benesh notation.
The ISTD do have a web site www.istd.org
The most complete dictionary of Cecchetti terms is by Rhonda Ryman published in 1998 by Dance Collection Press in Canada.
A book of photos of Cecchetti teaching Pavlova etc was also published in Canada a few years ago
His son (he had several) Grazioso also developed his fathers teaching I worked with the editor of the English version of his 2 volume book published in 1997 by Gremese.
Cecchetti is not only a method of teaching but also a style of ballet, which also has similarities with the Bournonville technique. You can trace a direct line back from Enrico Cecchetti to Beauchamp the first Maitre at the French Académie in 1661.
Best of luck with your article do let me know when it is published.