You can see the problem here: https://api.crossref.org/works?filter=from-pub-date%3A1993%2Cuntil-pub-date%3A1993&query.title=EFFECTS+OF+STANDARIDIZED+EXTRACTS+GK501%2C+FROM+GINKGO+BILOBA+L.%2C+G115+FROM+PANAX+GINSENG+C.A.+MEYER%2C+AND+THEIR+COMBINATION%2C+GINCOSAN+%28PHL-001701%29%2C+ON+THE+BRAIN+LEVELS+OF+BIOGENIC+MONOAMINES+AND+ON+THE+SERUM+CONTENT+OF+PROLACTIN%2C+GROWTH+HORMONE+AND&query.author=PETKOV removing the final AND makes the query answer properly.
