source: This makes it difficult to form an objective assessment of how effectively these have worked, either alone or together, and to evaluate appropriately the likely success of activity of this nature in the future. 
target: Mae hyn yn ei gwneud hi’n anodd i asesu’n wrthrychol pa mor effeithiol y mae’r rhaglenni hyn wedi gweithio, naill ai ar eu pennau eu hunain neu gyda’i gilydd, ac i werthuso’n briodol lwyddiant tebygol rhaglenni o’r fath yn y dyfodol. 