https://www.youtube.com/watch?v=h6i-QOik8SU&list=PLEE83FC1C1E35ADA7&index=3
https://www.youtube.com/watch?v=cUG-KcRLMAE&index=2&list=PLEE83FC1C1E35ADA7
http://conteudosdidacticosevt.blogspot.pt/2011/01/relogios-de-parede.html
https://www.youtube.com/watch?v=UrQA0Zf0sas
https://www.youtube.com/watch?v=NH8L0OOtdas
http://educacaotecnologica.2000pt.net/movimentos.htm
http://comevt.blogspot.pt/2012/03/o-movimento.html
http://evtembaiza.blogspot.pt/2011/06/esta-unidade-de-trabalho-pretendeu-num.html