It should be noted... (a little more formal)

  It should also be noted... (a little formal too)

  It should be mentioned...

  One can notice...

  Everybody can notice/realize...

  Anybody could notice...

  One must consider...

  It appears that...

  It should be pointed out that...

  It is possible to notice...

    And others, but they are not fit-all contexts.   You have to see some translated texts to get the hang of it. 

    Anyway some examples here.

http://www.linguee.com.br/portugues-ingles/search?source=auto&query=%E9+de+se+notar