What am I reading today?

An article from 1972. Characterization of the Oxidized and Reduced Zones in Flooded Soil. I can't believe you still need a subscription to view this article. How long do copyright protections exist for articles published prior to 1978?

The oxidized and reduced layers in flooded soil were characterized by vertical distribution of the oxidation-reduction (redox) potential and concentrations of manganous manganese, ferrous iron, sulfide, nitrate, and ammonium. Redox potential was measured with a special motor-driven assembly which advanced a platinum electrode at a rate of 2 mm/hour through the flooded soil profile. Vertical distribution of reduced forms of manganese, iron, and sulfur and of nitrate and ammonium was determined by freezing and slicing the flooded soil into segments 1 or 2 mm thick. The apparent thickness of the oxidized layer was different when evaluated by the distribution of the various components in the profile, with the sulfide profile indicating the thickest oxidized zone, the manganese profile indicating the thinnest oxidized zone, and the iron profile showing an intermediate thickness. The thickness of the oxidized layer increased with duration of flooding.