Merging zones in flow injection analysis: Part 6. Determination of calcium in natural waters, soil and plant materials with glyoxal bis(2-hydroxyanil) - Jacintho, Antonio Octavio; Zagatto, Elias Ayres Guidetti; Reis, Boaventura Freire dos; Pessenda, Luiz Carlos Ruiz; Krug, Francisco José (Analytica Chimica Acta, 1981)