No estoy seguro si + el indicativo

[dupond]

Hi everyone

I was looking at examples of how the phrase "no estoy seguro si" is used and all the examples I've seen use the indicative.

From http://context.reverso.net/traduccio...stoy+seguro+si

Es un volumen pequeño; no estoy seguro si lo han visto.
It's a little slim volume; I'm not sure if you've seen this.

Bien, no estoy seguro si necesita cirugía aún.
Well, I'm not sure if he needs surgery yet.

Ahora no estoy seguro si fue así.
Now I'm not sure I did.

Is this always the case? I was expecting that "no estoy seguro si" be used with the subjunctive, since phrases like "no creo que" take the subjunctive.

If "no estoy seguro si" can be used with the subjunctive, would it be another instance of the indicative showing more certainty in a given assertion than the subjunctive?


Thanks