Böhm used this work as part of his dissertation, submitted in 1951 (amended after submission), published in 1954.
[4] Since the language accepted only two kinds of expressions: fully parenthesized or without parenthesis, but with operator precedence, therefore the code of the compiler split into two parts.
[5] Böhm's parsing technique for expressions had only linear complexity.
It generated instructions to a structure similar to a binary tree.
It had no special constructs like user defined functions, control structures.