Correct transliteration of foreign Names with umlauts and other diacritics [duplicate]

Solution 1:

Spelling issues are usually handled by style guides, so there is no single correct answer.

For example, here's what the New York Times style guide says (or said in 2014):

Accent marks are used for French, Italian, Spanish, Portuguese and German words and names. For simplicity, use the marks uniformly with uppercase and lowercase letters, despite conventions that treat certain uppercase accents as optional. Do not use accents in words or names from other languages (Slavic and Scandinavian ones, for example), which are less familiar to most American writers, editors and readers; such marks would be prone to error.

The Public Editor's Journal

Thus, in the New York Times, you'd expect to see "René Descartes" but "Jons Jacob Berzelius" (rather than "Jöns"). Or for non-hypothetical example, "What to Eat and Where to See Roman Monuments in Nîmes", versus "A labyrinth of emotions from the Lodz ghetto" (not "Łódź").

Other newspapers seem to use a similar guideline, but many other publications do not. For example:

AMA Manual of Style:[...]Accent marks should always be retained in the following instances: Proper names: Dr Bönneman is a Pew Scholar in the Biomedical Sciences[...]

AP Stylebook: "Use accent marks or other diacritical marks with names of people who request them or are widely known to use them, or if quoting directly in a language that uses them[...]"

APA style: "[Reference list:] The best way to ensure that information is accurate and complete is to check each reference carefully against the original publication. Give special attention to spelling of proper names and of words in foreign languages, including accents or other special marks[...]"

The Chicago Manual of Style: "Foreign words, phrases, or titles that occur in an English-language work must include any special characters that appear in the original language. Those languages that use the Latin alphabet may include letters with accents (diacritical marks), ligatures, and, in some cases, alphabetical forms that do not normally occur in English[...]"

Wikipedia:Diacritical marks