A simple procedure for standard additions in flow injection analysis: Spectrophotometric determination of nitrate in plant extracts - Giné-Rosias, Maria Fernanda Georgina; Reis, Boaventura Freire dos; Zagatto, Elias Ayres Guidetti; Krug, Francisco José; Jacintho, Antonio Octavio (Analytica Chimica Acta, 1983)