Unexpected mailed survey response rates.
Riesenberg
Lee Ann
LA
Rosenbaum
Paula
P
Stick
Sheldon L
SL
D003625:Data Collection / Q000191:economics* / Q000379:methods; D004503:Education, Medical, Graduate; D006801:Humans; D009042:Motivation; D011177:Postal Service; D014040:Token Economy; D014481:United States