Find the product names that are colored 'white' but do not have unit of measurement "Handful".
select t1.product_name from products as t1 join ref_product_categories as t2 on t1.product_category_code = t2.product_category_code join ref_colors as t3 on t1.color_code = t3.color_code where t3.color_description = "white" and t2.unit_of_measure != "Handful"