search replace puts \1(space) in text

[isabelle1231]

I use Sigil to fix broken paragraphs. This without problems for some months. But lately I always the problem that sigil puts \1(space) in the text

Example text that needs fixing:

thought as</p>

<p class="calibre2">the shuttle

My result lately :

thought a\1 the shuttle

I use the following settings:
Find : [(a-z)]</p>\s+<p class="calibre2">
Replace: \1(space)
Match whole word only is unchecked and not highlighted
Match case is checked
Minimal matching is checked
Regular expression is checked
Direction All is checked

I've no problem in finding what I want to change but don't know why Sigil puts the result:

thought a\1 the shuttle

instead of

thought as the shuttle

I've been searching for some time now but I can't find what I need to change.

[Toxaris]

Change your find string:

([(a-z)])</p>\s+<p class="calibre2">

The parenthesis indicate that these entries need to be maintained. That is what the \1 refers to and will be replaced by.

[isabelle1231]

Thanks it worked. It was so simple. It is something that I won't forget anymore.