Heteroskedasticity Residual Plots

I am attaching three different residual plots. I am trying to determine whether heteroskedasticity is present. I don't believe I see any pattern indicative of heteroskedasticity (nonconstant variance). I know it can be difficult to detect - do you see any indication of this?

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... all other lag values should be statistically "cero". That is, all other values should fall within Bartlett's band of significance. Now if you have a non-cero value, then a periodic component on your residuals sequence is present and you should be worrying about non-stationary conditions on your original data, maybe periodicities. A final word should be pointed to ...