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+
+Relevant github issue: https://github.com/internetarchive/fatcat/issues/48
+
+
+## Investigate
+
+At least some of these DOIs actually seem valid, like
+`10.1026//1616-1041.3.2.86`. So shouldn't be re-writing them!
+
+    zcat release_extid.tsv.gz \
+        | cut -f1,3 \
+        | rg '\t10\.\d+//' \
+        | wc -l
+    # 59,904
+
+    zcat release_extid.tsv.gz \
+        | cut -f1,3 \
+        | rg '\t10\.\d+//' \
+        | pv -l \
+        > doubleslash_dois.tsv
+
+Which prefixes have the most double slashes?
+
+    cat doubleslash_dois.tsv | cut -f2 | cut -d/ -f1 | sort | uniq -c | sort -nr | head
+      51220 10.1037
+       2187 10.1026
+       1316 10.1024
+        826 10.1027
+        823 10.14505
+        443 10.17010
+        186 10.46925
+        163 10.37473
+        122 10.18376
+        118 10.29392
+        [...]
+
+All of the 10.1037 DOIs seem to be registered with Crossref, and at least some
+have redirects to the not-with-double-slash versions. Not all doi.org lookups
+include a redirect.
+
+I think the "correct thing to do" here is to add special-case handling for the
+pubmed and crossref importers, and in any other case allow double slashes.
+
+Not clear that there are any specific cleanups to be done for now. A broader
+"verify that DOIs are actually valid" push and cleanup would make sense; if
+that happens checking for mangled double-slash DOIs would make sense.