Cost of acquisition rules expanded to cover firm-to-company and proprietorship-to-company successions, applied retrospectively to affected years. The amendment substitutes the reference in the cost-of-acquisition provision to include transfers by succession from a firm to a company and from a sole proprietary concern to a company, thereby treating such transfers as subject to the rule that deems the asset's cost to be the cost at which the previous owner acquired it; the substitution is given retrospective effect to apply to the relevant assessment years specified in the amendment.