Geomorphic Characteristics of Drainage Ditches in Southern Minnesota, and the concept of a Two-Stage Ditch Design (Brad Hansen, Bruce Wilson, Joe Magner, and John Nieber)
"Archived copy"(PDF). Archived from the original(PDF) on 2007-08-01. Retrieved 2007-10-14.{{cite web}}: CS1 maint: archived copy as title (link)
Geomorphic Characteristics of Drainage Ditches in Southern Minnesota, and the concept of a Two-Stage Ditch Design (Brad Hansen, Bruce Wilson, Joe Magner, and John Nieber)
"Archived copy"(PDF). Archived from the original(PDF) on 2007-08-01. Retrieved 2007-10-14.{{cite web}}: CS1 maint: archived copy as title (link)