The Complete Works collection consists of several hundred improvised talks - 19 volumes available in English
Syntaxes of research
word1 word2: search on at least one of the two words.
+word1 +word2: search on both words.
"word1 word2": search on the expression between" ".
word*: searches on the beginning of the word, whatever the end of the word.
-word: the word behind - is excluded from the search.