The appraiser shall not assign, subcontract or transfer any portion of the work under his or her contract without written approval of the ROW Program Office. However, this does not prevent the contract appraiser from using other qualified appraisers to provide appraisal assistance. The PREAS contract appraiser's signature will be sole signature on the report. By signing the certification, the contract appraiser accepts responsibility for the entirety of the analyses and conclusion in the appraisal report. Other appraisers providing significant assistance must be named in the certification, and the nature of their assistance must be reported, but this does not have to appear in the certification.