Merging zones in flow injection analysis: Part 4. Simultaneous spectrophotometric determination of total nitrogen and phosphorus in plant material - Reis, Boaventura Freire dos; Zagatto, Elias Ayres Guidetti; Jacintho, Antonio Octavio; Krug, Francisco José; Bergamin Filho, Henrique (Analytica Chimica Acta, 1980)