Alois Hába, String Quartet No. 3, Mvt. III, 'cello, mm. 7-14 (five notations)
In this example, I've set the same passage five times: (a) uses two staves, where the upper staff sounds one quarter tone higher, (b) uses arrows to indicate raised pitches, (c) uses non-standard noteheads to indicate raised pitches, (d) uses Carrillo's pitch-class integer notation, and (e) uses quarter-tone accidentals. In my opinion, (c) and (d) come across as the least desirable strategies, and (e) is the easiest to read and the most practical for performance.