Bibliography of Robertson, G. P., by subject:

•	Spain -- Politics and government -- 1886-1931 (3)
•	Soil ecology -- Research -- Congresses (1)
•	Nitrogen cycle -- Caribbean area -- Congresses (1)
•	Atmospheric chemistry -- Congresses (1)
•	Ecology -- Congresses (1)
•	Biogeochemical cycles -- Congresses (1)
•	Soil ecology -- Methodology -- Congresses (1)
•	Economics (1)
•	Agricultural ecology -- Latin America -- Congresses (1)
•	Great Britain -- Economic conditions -- 1760-1860 (1)
•	Gases, Rare -- Measurement -- Congresses (1)
•	Nitrogen cycle -- Latin America -- Congresses (1)
•	Agricultural ecology -- Caribbean area -- Congresses (1)
•	Chemistry, Organic -- Laboratory manuals (1)