いまみたいにググって調べることもできないので本を買ったり税務署に聞きに行くしかないのですよね。
ぼくはなんとか暗号を解読して仕上げましたけど(^^;)

You couldn't Google this stuff then like you can now, so your only choices were to buy books about it and/or go to the tax office and ask. I managed to decipher the code and finish it up, though. (^^;)