fficient, the amount of tax due shall be determined by the director from such information as may be available . . . [and] may be estimated on the basis of external indices.??????) 3See, e.g., N.J. Stat. section 54:49-7. (??????If the commissioner finds that the taxpayer designs quickly to depart from this state or to remove therefrom his property, or any property subject to any state tax or to con