import re
p_text="""ref = <p class="references" style="font-size:15px">1. Mcminn. (2003). Last's Anatomy. Elsevier Australia. ISBN:0729537528. <a href="http://books.google.com/books?vid=ISBN0729537528">Read it at Google Books</a> - <a href="http://w...content-available-to-author-only...n.com/gp/product/0729537528">Find it at Amazon</a><br>
2. Netter, F. H. (2019). Atlas of human anatomy. Philadelphia, PA: Elsevier.</p>"""
result = list(map(int, re.findall(r"(?<![^\s>])([0-9]+)\. ", p_text)))
print(result)

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