- http://www.agendaweb.org/verbs/present-continuous/index.html
- http://www.carmenlu.com/first/grammar/presentcont17.htm
- http://www.montsemorales.com/gramatica/PresCont0.htm
- http://eslgamesworld.com/members/games/grammar/present%20tenses/present%20tenses%20snakes%20and%20ladders.html
- https://www.ego4u.com/en/cram-up/tests/present-progressive-1
