Given the scarcity of free PDFs, many researchers buy a used paperback (available on AbeBooks or Amazon for $25–40) and scan the relevant chapters. This is often faster than hunting for a corrupted PDF on Academia.edu.

is the most comprehensive as it includes scholarship on the post-independence era up to Singapore's 40th anniversary. Google Books A History of Modern Singapore, 1819-2005 - Amazon.com

Turnbull’s index is famously detailed. Use it to track specific figures (like Tan Tock Seng or David Marshall).