Neb. Rev. Stat. §§ 16-618
Any improvement district created pursuant to section 16-617 shall include only portions of different streets, or portions of alleys, or portions of each, which abut or adjoin so that such district, when created, makes up one continuous or extended street or more, except that the district may include a cul de sac, any street, alley, or portion thereof which is closed at one end or which connects with only one other existing street, alley, or portion thereof. Any improvement district may include portions of different streets, or portions of different alleys, or portions of each, if they abut or connect with each other, or if the several portions abut on pavement or gravel already laid, or any other of improvements already laid.
Neb. Rev. Stat. §§ 16-618