Если бы я знал мистера Робертсона,

Если бы я знал мистера Робертсона, я бы поговорил с ним.
Если бы Ричард был здесь, он дал бы вам другой совет.
Если бы я знал, что Смиты были тогда в Париже, я бы зашел к ним.

Результаты (английский) 1:

If I knew Mr. Robertson, I would have talked to him.If Richard was here, he would have given you another tip.If I knew that the Smiths were then in Paris, I would have gone to them.

Результаты (английский) 2:

If I knew of Mr. Robertson, I would talk to him.
If Richard were here, he would have given you another advice.
If I knew that Smith was then in Paris, I would have gone to them.

Результаты (английский) 3:

If I knew Mr. T. Robertson, I would have talked with him.
if Richard has been here, he would have given you a different council.
if I knew that Смиты were then in Paris, I would have gone to them.