CREATE TABLE table_name_36 (country VARCHAR, year_opened VARCHAR, span_feet VARCHAR, material VARCHAR, span_metres VARCHAR)
Which country's material was concrete when the span metres were less than 270, span feet is more than 837, and the year opened was 1943?
SELECT country FROM table_name_36 WHERE material = "concrete" AND span_metres < 270 AND span_feet > 837 AND year_opened = "1943"