if I had known
Si yo hubiera sabido más sobre su carácter, no habría confiado en él.
If I had known more about his character, I would not have trusted him.
Si yo hubiera sabido su dirección, le habría mandado una carta.
If I had known his address, I would have sent him a letter.
Si yo hubiera sabido la verdad, te la habría dicho.
If I had known the truth, I would have told you.
Si yo hubiera sabido su dirección, habría podido visitarla.
If I had known her address, I could have visited her.