The usual style for HTML attributes is to have no spaces around the "=" sign, like this:

&lt;a href="https://www.authorea.com/users/5574/articles/6800/_show_article" target="_blank">

(You had it correct for the target="_blank" attribute.)

(By the way, in programming code, you _do_ generally want spaces around the "=" sign, for example:

    a = 8 * 9

)