Perhaps you should try some spelling variations:
"block spaces" » "fock spaces", "bloch space", "fock space", "bloch spaces", "block sparses", "bloch spacess"
"black space" » "slack space", "blank space", "black spruce"
"block space" » "bloch space", "block sparse", "bloch spaces"

You may be able to get more results by adjusting your search query.

• If you are trying to use Boolean operators, they must be ALL CAPS: (("black space") OR ((("block space") OR ("block spaces")))).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"black space\") or (((\"block space\") OR (\"block spaces\"))))".
• Removing quotes may allow a broader search: (( black space ) or ((( block space ) OR ( block spaces )))).
• Adding a wildcard symbol may retrieve word variants: (("black space") or ((("block space") OR ("block spaces"))))*.