Clarke, H., & Lapper, i. I. (1983). Os vikings. Verbo.
Lua i Stíl Chicago (17ú heag.)Clarke, Helen, agus il. Ivan Lapper. Os Vikings. Verbo, 1983.
Lua MLA (8ú heag.)Clarke, Helen, agus il. Ivan Lapper. Os Vikings. Verbo, 1983.
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