http://www.archtoolbox.com/materials-systems/vertical-circulation/escalators.html
http://continuingeducation.construction.com/article.php?L=14&C=455&P=1
http://www.kone.us/search-results.aspx?search=escaltor (Then select first link to download which is a {.PDF} )
http://inventors.about.com/library/inventors/blescalator.htm
https://mail.google.com/mail/u/0/?pli=1#inbox/14898e6945a15c77
http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CB4QFjAA&url=http%3A%2F%2Fwww.bd.gov.hk%2Fenglish%2Fdocuments%2Fcode%2FBWLE2011e.pdf&ei=hGIgVOO3A-qJsQSO_YLgDw&usg=AFQjCNH64-PIOOOZGnxddgpItQzj8gJr6g&sig2=jWGDB0fQB5wT_7qxxjRY4g
