looking for help understanding this old physics paper.

pic related. this paper is from 1971 and Wikipedia says it is the paper that established that string theories need more than the normal number of dimensions of space. (https://en.wikipedia.org/wiki/Bosonic_string_theory#cite_note-PR-1)

i ask because i can sort of follow what Polchinski says in his textbook but i find myself seeking a better explanation. Zwiebach and Green-Schwarz-Witten skip any explanation, and googling only yields SE posts from shill Lubos Motl which are characteristically "oh you're a brainlet haha me lubos"... so i was looking for a good primary source. as far as i can tell this paper doesn't explain much at all except by jumping from one obscure equation to another and then declaring bosonic string theory needs 26 dimensions due to the not-filled-in details.

anybody have any insight on how to understand this?

(PS: the author, Claud Lovelace, was a crazy motherfucker)