Read this: Although the Estonian orthography is generally guided by phonemic principles, with each grapheme corresponding to one phoneme, there are some historical and morphological deviations from this: for example preservation of the morpheme in declension of the word (writing b, g, d in places where p, k, t is pronounced) and in the use of 'i' and 'j'.[clarification needed] Where it is very impractical or impossible to type š and ž, they are substituted with sh and zh in some written texts, although this is considered incorrect. Otherwise, the h in sh represents a voiceless glottal fricative, as in Pasha (pas-ha); this also applies to some foreign names.

What type of deviations are there from the single phoneme to each grapheme general principle?
What is the answer? (If it cannot be answered, return "unanswerable")
some historical and morphological deviations