1 ) ▁ ▁where ▁n ▁is ▁an ▁integer . ▁Usually ▁one ▁adds ▁boundary ▁conditions : ▁for ▁example , ▁the ▁functions ▁an ▁could ▁be ▁periodic : ▁an ▁= ▁an + N ▁for ▁some ▁N , ▁or ▁could ▁van ish ▁for ▁n   ≤   0 ▁and ▁n   ≥   N . ▁ ▁The ▁Vol terra ▁lattice ▁was ▁originally ▁stated ▁in ▁terms ▁of ▁the ▁variables ▁R n ▁= ▁– log ▁an ▁in ▁which ▁case ▁the ▁equations ▁are ▁ ▁R n ' ▁= ▁e − R n – 1 ▁– ▁e − R n + 1 ▁ ▁References ▁▁▁▁ ▁Category : In te gra ble ▁systems <0x0A> </s> ▁R ED I RECT ▁ 1 8 9 1 ▁United ▁States ▁House ▁of ▁Representatives ▁elections # Special ▁elections ▁South ▁Dak ota ▁ 1 8 9 1 ▁at - large ▁South ▁Dak ota ▁ 1 8 9 1 ▁at - large ▁ 1 8 9 1 ▁at - large ▁Special ▁South ▁Dak ota ▁at - large ▁Special ▁United ▁States ▁House ▁of ▁Representatives ▁at - large ▁Special ▁United ▁States ▁House ▁of ▁Representatives ▁ 1 8 9 1 ▁at - large <0x0A> </s> ▁Water ▁supply ▁and ▁san itation ▁in ▁R w anda ▁is ▁character ized ▁by ▁a ▁clear ▁government ▁policy ▁and ▁significant ▁don or ▁support . ▁In ▁response ▁to ▁poor ▁sust ain ability ▁of ▁rural ▁water ▁systems ▁and ▁poor ▁service ▁quality , ▁in ▁ 2 0 0 2 ▁local ▁government ▁in ▁the ▁Northern ▁By um ba ▁Province ▁contract ed ▁out ▁service ▁provision ▁to ▁the ▁local ▁private ▁sector ▁in ▁a ▁form