You can search for parsing techniques that were available and practical in 1965: recursive descent, the shunting yard algorithm, and operator precedence parsing[0]. LR(k) parsing was described by Knuth in 1965, but I don't think it was considered practical yet due to the memory required by LR(1) tables.
[0]: 1963 operator precedence description: https://dl.acm.org/doi/10.1145/321172.321179