2007,W. Schmitz,The Violet Catastrophe, ISBN 1846930502, page 33-34:
She was all right. The abuse she was suffering wouldn't hurt her. The bright sun would forget all about it. The smoggy sky would turn brown studies to gold. (What crap.)
Verville, author of Moyen de Parvenir, and others equally well known, among whom we will specially mention the Sieur Descartes, because he was a melancholy genius, and devoted himself more to brown studies than to drinks and dainties, a man of whom all the cooks and confectioners of Tours have a wise horror, shom they despise, and will not hear spoken of, and say, "Where does he live? if his name is mentioned.
2011,Stella Gibbons,White Sand and Grey Sand, ISBN 1448103401, page 275:
She was pensive, she drooped; more than once she sighed unromantically through her nose; she went off into brown studies;