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infrequent is the most popular phrase on the web.

unfrequent 1333,000 results on the web	infrequent 116,200,000 results on the web More popular!
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It doesn't look like this phrase is very popular! The search could not find any examples on the internet.	Rash was most frequently mild to moderate, generally macular to maculopapular or erythematous, mostly occurred in the second week of therapy, and was infrequent after week 4. The use of the product in both types of chicken is infrequent as coccidiosis is mainly controlled by good hygiene and coccidiostats or vaccines. However, such reports have been infrequent. Progressive decreases after 8 weeks of therapy were infrequent. Nevertheless, misuse of lighters, especially by young children, is not infrequent and must be considered when assessing the safety of such products. Information regarding significant factors, including unusual or infrequent events or new developments, materially affecting the issuer's income from operations, indicating the extent to which income was so affected. This adverse reaction is infrequent in patients with early HIV disease and blood tests may be performed less frequently. Mild winters in which animals do not need to be housed at night are not infrequent in Sardinia.

unfrequent

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infrequent

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It doesn't look like this phrase is very popular! The search could not find any examples on the internet.

Rash was most frequently mild to moderate, generally macular to maculopapular or erythematous, mostly occurred in the second week of therapy, and was infrequent after week 4.
The use of the product in both types of chicken is infrequent as coccidiosis is mainly controlled by good hygiene and coccidiostats or vaccines.
However, such reports have been infrequent.
Progressive decreases after 8 weeks of therapy were infrequent.
Nevertheless, misuse of lighters, especially by young children, is not infrequent and must be considered when assessing the safety of such products.
Information regarding significant factors, including unusual or infrequent events or new developments, materially affecting the issuer's income from operations, indicating the extent to which income was so affected.
This adverse reaction is infrequent in patients with early HIV disease and blood tests may be performed less frequently.
Mild winters in which animals do not need to be housed at night are not infrequent in Sardinia.