Access the FASB Accounting Standards Codification at the FASB website (www.fasb.org). Determine each of the following: 

1. The specific eight-digit Codification citation (XXX-XX-XX-X) that discusses depreciation as a systematic and rational allocation of cost rather than a process of valuation. 

2. The specific nine-digit Codification citation (XXX-XX-XX-XX) that involves the calculation of an impairment loss for property, plant, and equipment. 

3. The specific nine-digit Codification citation (XXX-XX-XX-XX) that provides guidance on accounting for a change in depreciation method. 

4. The specific eight-digit Codification citation (XXX-XX-XX-X) that indicates goodwill should not be amortized.