Neb. Rev. Stat. § 43-105

(1) If consent is not required of both parents of a child born in lawful wedlock if living, the surviving parent of a child born in lawful wedlock, or the mother or mother and father of a child born out of wedlock, because of the provisions of subdivision (1)(b) of section 43-104 , substitute consents shall be filed as follows: (a) Consent to the adoption of a minor child who has been committed to the Department of Health and Human Services may be given by the department or its duly authorized agent in accordance with section 43-906 ; (b) When a parent has relinquished a minor child for adoption to any child placement agency licensed or approved by the department or its duly authorized agent, consent to the adoption of such child may be given by such agency; and (c) When consent cannot be given as provided in section 43-104 , consent shall be given by the guardian or guardian ad litem of such minor child appointed by a court, which consent shall be authorized by the court having jurisdiction of such guardian or guardian ad litem. (2) Substitute consent provisions of this section do not apply to a biological father whose consent is not required under section 43-104.22">43-104.22 or subsection (5) or (6) of section 43-104 .